Siblings in families of children with chronic disorders: a model of risk and protective factors

Abstract

Objective

We empirically tested a family systems model’s ability to explain variance in psychosocial adjustment among siblings of children with chronic developmental and physical disorders (CDs). The model included the impact of CD severity, family social support, parental mental health, and parent–sibling communication quality. We hypothesized that family social support would moderate the relationship between CD severity and parent mental health, and that sibling-reported communication quality with their parents would mediate the relationship between parent mental health and sibling psychosocial adjustment.

Methods

We used baseline data from a sibling intervention trial (SIBS-RCT) comprising 288 families with siblings aged 8–16 years and their parents, recruited from health services and user organizations. Parents reported CD severity, parental mental health, and family social support. Siblings self-reported their psychosocial adjustment, including mental health, CD-related adjustment, quality of life, and prosocial behavior. We employed structural equation modeling to test the hypothesized relationships.

Results

Higher parent–sibling communication quality was significantly associated with better sibling-reported quality of life and more prosocial behavior. Lower levels of paternal depression were significantly associated with better sibling-reported quality of life and mental health, whereas maternal depression was not. We did not find support for the hypothesized mediating and moderating pathways for family social support and parent–sibling communication.

Conclusions

The findings highlight the importance of addressing paternal mental health and parent–sibling communication in promoting sibling psychosocial adjustment. Future studies should use comprehensive, multi-informant approaches and consider the complex interplay of family factors in the context of childhood CD.

Extensive research has shown that siblings of children with chronic developmental and physical disorders (hereafter CDs) are at risk of poorer psychosocial adjustment, including more emotional and behavioral problems, less social support, and lower quality of life than their peers (Kirchhofer et al., 2022; Pinquart, 2023; Wolff et al., 2022). CDs are enduring conditions that affect individuals from early childhood and across the lifespan (World Health Organization, 2023), and include a wide range of physical, developmental, and/or psychological conditions, such as neuromuscular diseases, autism spectrum disorders, and attention-deficit/hyperactivity disorder (ADHD). Despite their diversity, CDs share long-lasting effects on the individual’s health and development, and often require ongoing management and care, affecting parents and siblings as well.

Siblings of children with a wide range of CDs (herein, siblings) are at risk of developing psychosocial problems. A recent meta-analysis found elevated levels of internalizing, externalizing, and total behavior problems for siblings of children with chronic physical health conditions (g=.13–22; Pinquart, 2023). Other reviews have shown siblings of individuals with neurodevelopmental disorders to be at increased risk of stress, internalizing problems, externalizing problems, and overall poorer well-being (Wolff et al., 2022, 2023a). Therefore, in the present study examining sibling risk, we apply a dimensional (i.e., nondiagnostic-categorical) approach and include a broad range of CDs despite their diversity in etiology and course.

Risk and protective factors

Sibling psychosocial adjustment is shaped by a combination of risk and protective factors (Wolff et al., 2022). Risk factors for siblings can arise directly from the CD, such as witnessing epileptic fits, facing physical or verbal threats, and worrying about the prognoses. Previous studies show strong associations between CD severity and sibling mental health problems, both for chronic medical and neurodevelopmental disorders (Vermaes et al., 2012; Wolff et al., 2022). In the current study, disorder severity is operationalized by the Developmental Behavior Checklist Primary Carer Version (DBC-P; Einfeld et al., 2002). Severity refers to the degree of functional impairment and the need for support in everyday life. This includes difficulties with age-appropriate self-care, behavioral, and emotional challenges such as mood disturbances (e.g., depression, anxiety, delusions), and disruptive behaviors (e.g., aggression, rages, or age-inappropriate actions; Einfeld et al., 2002).

CD severity is associated with parent mental health as well (Scherer et al., 2019). Sibling risk can arise indirectly due to differential parental treatment (Kelada et al., 2022), limited parental time, strained caregiving due to treatment demands, and parental stress and mental health problems (Atkins & Padgett, 2024; Cohn et al., 2020). Parental mental health problems such as depression have also been linked to increased risk for siblings (Tudor et al., 2018). Depression can affect parents’ ability to respond to and acknowledge emotions adequately and attend to siblings’ needs (Lovejoy et al., 2000).

Because siblings of children with CDs are at higher risk for poor outcomes, mapping sibling mental health is an essential part of understanding their overall psychosocial adjustment. This may help identify clinically relevant mental health concerns and inform sibling interventions. However, in sibling research, general mental health assessments may not sufficiently capture the unique challenges siblings face. Utilizing more sibling-specific measures of adjustment, such as the Negative Adjustment Scale (NAS; Lobato & Kao, 2002), measuring interpersonal relationships, intrapersonal responses, fear, and communication, can provide deeper insight into the nuances of the sibling experience beyond mental health symptoms (Veerman et al., 2025).

Research across a wide range of CDs has also found positive impacts for siblings, such as increased prosocial behavior and mentalizing skills (Orm et al., 2022c; Pinquart, 2023) and interestingly suggesting prosocial behavior may be viewed as an adaptive outcome rather than a mere consequence of the caregiving role (Orm et al., 2022b). Still, positive sibling outcomes such as quality of life, self-esteem, social relationships, and prosocial behavior, are understudied in the field (Wolff et al., 2022). A multidimensional assessment approach, including these adaptive outcomes, can provide a richer understanding of how siblings navigate their social environments and manage their unique family circumstances, offering valuable information that mental health outcomes alone cannot capture.

Protective buffers against CD-related stress include the amount of support available to the family from formal or informal resources and family communication (Incledon et al., 2015; Kirchhofer et al., 2022). Social support is a significant protective factor in both the general population and for individuals with CDs (Incledon et al., 2015; Uchino, 2009). Among siblings of children with CDs, emotional and informational support has been linked to fewer behavioral problems and serves as a protective factor for mental health (Incledon et al., 2015; Kirchhofer et al., 2022). Open and emotionally supportive communication with parents can help siblings navigate emotional and social challenges (Haukeland et al., 2015). However, in many families with childhood CDs, family communication is characterized by less warmth and higher levels of hostility (Murphy et al., 2017, 2018). This dynamic may pose a particular risk because siblings often cope with their emotions independently and are less inclined to confide in their parents about their struggles (Haukeland et al., 2015).

Model frameworks for sibling psychosocial adjustment

According to family systems theories, family members influence each other reciprocally, at both the dyadic (e.g., sibling–sibling, mother/father–child dyads) and systemic levels (Minuchin, 2018; Watson, 2012). This framework can support our understanding of family experiences of living with childhood CD, emphasizing the interplay between factors such as the severity of the disorder, family resources, and individual perceptions. Although sibling risk and protective factors are multifaceted, little research has explored how they interact dynamically or bidirectionally to influence sibling psychosocial adjustment.

One example, however, is the model presented by Tudor et al. (2018), where they sought to address this limitation and found maternal depressive symptoms and disorder severity to be a key sibling risk factor in their good-fitting path analysis model. In their model, greater disorder severity and problem behaviors were expected to increase maternal stress and depression and differential attention toward children, and poorer sibling relationship quality. These factors were predicted to negatively impact siblings’ psychological functioning assessed through clinical factors like sibling internalizing and externalizing symptoms and social abilities. Higher disorder severity and problem behaviors predicted increased maternal depression, stress, and differential attention toward children and maternal depression predicted siblings’ internalizing symptoms, demonstrating that sibling functioning is better understood as an outcome of many interrelated predictive family pathways rather than a direct outcome of their brother or sister’s special needs. However, in addition to an autism-specific sample, their study relied on maternal reports, leaving a multi-informant approach across a broader range of CDs unexplored. Differences in how mothers and fathers perceive and are affected by the CDs (Cohn et al., 2020; Zahl et al., 2024) may uniquely affect sibling outcomes, highlighting the importance of considering distinct family roles.

A proposed family model

For the current study, we developed a family model to explain variation in the psychosocial adjustment of siblings of children with CDs (see Figure 1 for the proposed model). The model is inspired by Tudor et al. (2018), family system theories (Minuchin, 2018; Watson, 2012), and recent reviews of risk and resilience factors for siblings of children with CDs, including siblings of children with chronic medical disorders and neurodevelopmental disorders (Kirchhofer et al., 2022; Pinquart, 2023; Wolff et al., 2022). In addition to the direct impact of disorder severity on sibling psychosocial adjustment (path A), the model proposes that CD severity may also indirectly impact sibling psychosocial adjustment through its effect on parental mental health (path B*C). The impact of parental mental health on siblings’ psychosocial adjustment may operate both directly (path C) and indirectly, through parent–sibling communication quality (path E*F).

Figure 1.

A proposed family model of sibling risk and protective factors.

We propose that parent–sibling communication may act as a conduit through which parent mental health, specifically depressive symptoms, can directly influence sibling outcomes (path E*F). Therefore, in terms of this key pathway in our model, we propose that parent–sibling communication quality may function as an intermediate variable between parental depression and sibling psychosocial adjustment. We also propose parent depression as an intermediate variable due to considerable empirical evidence that it is affected by having a child with a CD (Atkins & Padgett, 2024; Cohn et al., 2020). Thus, disorder severity may impact sibling psychosocial adjustment through its cascading effects on parental depression (path B) and parent–sibling communication (path B*E*F).

We tested the following hypotheses for the proposed conceptual model; (a) CD severity will be related to parental depression with higher CD severity associated with higher parental depression (path B); (b) family social support will buffer against (i.e., moderate) the relationship between CD severity and parental depression (path D); (c) parental depression will be related to sibling psychosocial adjustment, expecting more parental depression to increase sibling mental health problems and CD-related adjustment problems, and negatively impact quality of life and prosocial behavior (path C); (d) parental depression will be related to parent–sibling communication quality, expecting more parental depression to be associated with poorer parent–sibling communication quality, and that communication will mediate the relationship between parental depression and sibling psychosocial adjustment (path E*C). Finally, (e) CD severity will be directly related to siblings’ psychosocial adjustment (path A), and also partially sequentially mediated by parental depression (path B*C) and parent–sibling communication (path B*E*F). As for differences between mothers and fathers, we explored this openly by creating two models, one for mothers and one for fathers. We did not have specific hypothesis that the model would be different for different sibling ages or gender groups. However, we included sibling age, gender, and parental educational level as covariates, as previous research has found that these variables are related to psychosocial adjustment in siblings (Martinez et al., 2022; Vermaes et al., 2012).

Methods

The current study utilizes baseline data from a sibling intervention trial conducted between 2019 and 2023 (SIBS-RCT; Fjermestad et al., 2020). The purpose of the intervention was to prevent sibling mental health problems and improve parent–sibling communication through SIBS, a 5-session manual-based group intervention. All participating families had at least one child aged 0–18 years with a CD. The inclusion CDs were any neurodevelopmental disorder, chronic medical disorders including cancer, congenital heart disease, diabetes, and eating disorders. The child with a CD had to receive specialist and/or municipal (community-based) health services as indicator of severity and for cross-checking of diagnosis with clinical registries. The participating families also had to have a sibling aged 8–16 years who did not have a CD.

Participants

A total of 288 siblings and their parents consented and were recruited to the trial. Sibling age was M = 10.5 years (SD = 2.1, range = 8–16), and age of the child with a CD was M = 10.5 (SD = 3.4, range = 3–18), mother age = 42.3 (SD = 5.4) and father age = 44.9 (SD = 5.8). For more demographic information on the sample and included CD, see Table 1.

Table 1.

Participant demographic information.

	Percent
Siblings’ sexa
Girls	55.2
Boys	44.8
Child with diagnosis’ sexa
Girls	36.6
Boys	63.4
Total distribution of primary diagnoses
ADHD	26.0
Rare disorderb	18.0
Emotional and conduct disorder	3.5
Autism	14.9
Asperger syndrome	11.8
Intellectual disability disorder	2.4
Somatic disorder	1.0
Down syndrome	10.0
Tourette’s syndrome	4.8
Eating disorders	4.5
Cerebral palsy	2.4
Specific developmental disorders	.7
Mothers’ highest education
Primary/secondary school	3.4
Highschool	18.2
University less than 4 years	32.2
University more than 4 years	46.2
Fathers’ highest education
Primary/secondary school	6.5
Highschool	32.0
University less than 4 years	23.4
University more than 4 years	38.1
Family economy
Very poor	.4
Poor	6.4
Neither good nor poor	28.9
Good	51.1
Very good	13.2
Family constellation
Living with both parents	80.4
Mostly with mother	17.9
Mostly with father	1.3
With other caretakers	.4
Children in the household
Two	56.4
Three	31.4
Four	7.6
Five	3.0
More than five	1.7
Sibling younger than child with diagnosis	51.6
Sibling older than child with diagnosis	42.6
Twins	6.0
Ethnicity
European	91.9
Asian	2.4
African	2.4
Other	3.3

Note. All demographic variables are parent reported, total do not equal N = 288 due to missing responses on demographics. CD diagnoses were cross checked with clinic registry. Family economy categories are parent self-reported perceived family economy. Hence, it is a measure of perceived economic safety and stability rather than an objective measure of family income.

^aThe Norwegian common term for sex and gender does not distinguish between sex and gender, the option of “other” was provided in the form. Note. CD = Chronic disorder; ADHD = Attention-deficit/Hyperactivity Disorder; SD = standard deviation; M = mean.

^bRare disorders are defined as affecting fewer than 1 out of 2,000 people and include in this sample.

Procedures

The participants were recruited through primary and specialist health care services where the child with a CD was treated, user organizations for different CDs, and via adverts online and in waiting areas in the seven included RCT sites. Families signed up for the study electronically and were assessed for eligibility by research coordinators. All participants were given age-appropriate information about the study and informed that they could withdraw from the study at any time. Parents provided consent on behalf of the children under 16 years old. Adolescents 16 years and older actively consented. The study was approved by the Regional Committees for Medical and Health Research Ethics (REK; No. 321027). Siblings, mothers, and fathers completed separate online questionnaire packages after being enrolled into the trial. Baseline data are available on request. For more information on the purpose and procedures of the trial, see Fjermestad et al. (2020).

Measures

Parent-reported measures

Parent mental health was measured with the Symptom Checklist-90-Revised (SCL-90-R; Derogatis & Unger, 2010). The SCL-90-R includes nine primary symptom scales of which the 13-item depression subscale was used in this study (herein SCL-90-Rdep). Responses are given on a 5-point Likert scale with responses ranging from 0 = not at all to 4 = very much, with higher total score reflecting more depression symptoms. The SCL-90-Rdep demonstrated good reliability, with α=.97 for mothers and fathers.

Social support was measured with the Family Support Scale (FSS; Dunst et al., 1986), an 18-item questionnaire that measures the amount of perceived support available to parents of children with CD by various formal and informal sources. Responses are given on a five-point Likert scale with responses ranging from 0=not available to 4 = extremely helpful where higher scores indicate greater amounts of support. The FSS measures support from family, friends, social groups, and professional service providers. We used the total score in this study. The FSS demonstrated acceptable reliability, with α=.67 for mothers and .77 for fathers.

Severity of the CD was measured with the 96-item DBC-P (Einfeld et al., 2002). The DBC-P is a parent-reported assessment tool of behavioral and emotional symptoms in children aged 4–18 years and gives an indication of the perception of CD severity. Responses are given on a 3-point Likert scale with responses ranging from 0=untrue to 2=very/often true, with answers reflecting to what degree the statement is considered true for their child with CD, with higher scores reflecting more behavioral and emotional symptoms. The Total Behavior Problem Score is the cumulative score of five subscales, which was used in this study. The DBC-P demonstrated good reliability, with α=.94 for mothers and fathers.

We asked both mothers and fathers to complete the parent-reported measures.

Sibling-reported measures

Parent–sibling communication was measured with the Parent-Child Communication Scale (PCCS) and reported by siblings, which measures the siblings’ rating of the quality of communication with their parents (Orm et al., 2022a). Responses are given on a five-point Likert scale with responses ranging from 1 = never to 5 = always. Higher values indicate an open/good communication between parent and child as experienced by the child. The PCCS demonstrated good reliability, with α=.83 for siblings’ ratings of mothers and .84 for siblings’ ratings of fathers.

Sibling mental health and prosocial behavior were measured by the Strengths and Difficulties Questionnaire (SDQ; Goodman, 2001) and completed by the sibling. A digital version of the official Norwegian SDQ was used (with permission from youthinmind.org). The 25-item questionnaire covers five domains including emotional, conduct, hyperactivity-inattention, and peer problems, making up the total difficulties score used in this study, as well as a prosocial behavior subscale which is reported separately. Responses are given on a scale ranging from 0 = not true to 2 = certainly true. The SDQ demonstrated good reliability, with α=.80 for the total difficulties scale.

Quality of life was measured with the Kinder Lebensqualität Fragebogen (KINDL; Ravens-Sieberer & Bullinger, 1998) and completed by siblings. This 24-item questionnaire represents a function-based indicator of well-being that goes beyond mental health symptoms and covers four components with the subscale’s psychological well-being, social relationships, physical function, and everyday life activities, each with 9–11 items. Responses are given on a five-point Likert scale with responses ranging from 1 = never to 5 = always. We used the total score in this study. The KINDL demonstrated good reliability, with α=.88 for the total scale.

The impact of the CD on siblings and their adjustment to the family was measured with the NAS (Lobato & Kao, 2002), a modified version of the Sibling Perception Questionnaire (Sahler & Carpenter, 1989) with 16-items measuring interpersonal relationships, intrapersonal responses, fear, and communication. Responses are given on a 4-point scale with responses ranging from 1=never to 4 = a lot. Higher scores indicate poorer adjustment to the CD as a sibling. The NAS demonstrated acceptable reliability, with α=.79 for the total scale.

Data analytic plan

We used structural equation models to test the model presented in Figure 1, for each sibling outcome and for mother and father responses separately. Each model included sibling gender, sibling age, and parent education as covariates affecting sibling outcome. Because of the modest sample size, we did not run multi-group analysis with sibling age, gender, or parent education. We also estimated the means for measured variables. In addition to direct paths, we calculated three indirect effects on sibling outcomes: (a) Parental mental health through communication (path E * path F); (b) CD severity through parental mental health and communication (path B * path E * path F); and (c) CD severity through parental mental health (path B * path C). As the indirect effects are estimated as products of parameters, confidence limits were obtained by nonparametric bootstrapping over 1,000 bootstrapped samples. We obtained bias-corrected and accelerated 95% confidence limits. Models were estimated using R, version 4.1.2 (R Core Team, 2021) using the package lavaan version 0.6-15 (Rosseel, 2012) using Full Information Maximum Likelihood (FIML) algorithm, as there were missing data. Model fit was assessed using χ², Root Mean Square Error of Approximation (RMSEA) and 90% confidence limits, Comparative Fit Index (CFI), Tucker–Lewis Index (TLI); and Standardized Root Mean Square Residual (SRMR).

Results

The most frequent CDs were ADHD, rare disorders (i.e., prevalence <1 out of 2,000), autism, Asperger syndrome, and Down syndrome (Table 1). Siblings in our study reported elevated mental health difficulties on the SDQ (boys = 9.79, girls = 9.84) compared with norms for Danish children aged 10–12 years¹ (boys = 6.02, girls = 5.27) (Niclasen et al., 2012). A larger than expected proportion of siblings were in the at-risk range (80th–90th percentile; boys = 16.5%, girls = 21.1%) and clinical range (90th+percentile; boys = 25.3%, girls = 33.3%). The means for sibling-reported communication with parents and negative adjustment closely aligned with what has been observed in other studies focusing on siblings of children with CDs (Lobato & Kao, 2002; Orm et al., 2022a). Parent depression was also above the normative mean for a nonclinical Norwegian population (.34; Derogatis & Unger, 2010), suggesting that parents in our sample may experience a higher depression compared to the general adult Norwegian population. Additionally, the average baseline level of perceived disorder severity was slightly above the clinical threshold for emotional and behavioral difficulties according to mothers, but slightly below the threshold according to fathers (46; Einfeld et al., 2002). Means for all the study measures and response rates are presented in Table 2.

Table 2.

Baseline measures for sibling- and parent-reported outcomes.

Informant	Scale	N a	Mean	SD	Min	Max	Range
Sibling
	Mental Health (SDQ total)	214	9.82	5.41	.00	30.00	30.00
	Negative Adjustment to the CD (NAS)	189	2.14	.45	1.25	3.69	2.44
	Quality of Life (KINDL)	189	93.28	12.32	56.00	118.00	62.00
	Prosocial Behavior (SDQ subscale)	214	8.41	1.39	3.00	10.00	7.00
About Mother	Communication Quality (PCCS)	201	32.13	5.55	16.00	40.00	24.00
About Father	Communication Quality (PCCS)	197	27.57	6.27	8.00	38.00	30.00
Parents
Mothers
	Disorder severity (DBC-P)	203	48.29	24.13	1.00	115.00	114.00
	Family Social support (FSS)	202	16.68	6.63	2.00	36.00	34.00
	Mental Health (SCL90-Rdep)	204	.97	.69	.00	3.46	3.46
Fathers
	Disorder severity (DBC-P)	133	42.00	22.58	1.00	107.00	106.00
	Family Social support (FSS)	134	18.25	7.41	2.00	37.00	35.00
	Mental Health (SCL90-Rdep)	125	.55	.57	.00	2.54	2.54

Note. SD=Standard Deviation; SDQ=Strength and Difficulties Questionnaire; NAS=Negative Adjustment Scale; KINDL=Kinder Lebensqualität Fragebogen; PCCS=The Parent-Child Communication Scale; DBC-P=The Developmental Behavior Checklist Primary Carer Version; SCL90-Rdep=Symptom Checklist Revised depression subscale; FSS=Family Support Scale.

^a N represents respondents; however Full Information Maximum Likelihood (FIML) algorithm was used to estimate missing values.

Sibling quality of life

For all sibling outcomes, the results from all individual paths in the model are presented in Tables 3 and 4, for mothers and fathers separately. The model with father-reported variables as predictors of sibling-reported quality of life showed good model fit (χ² (14 df)=14.33, p = .501, CFI = .999, TLI = .998, RMSEA = .008, 90% CI [.000, .058], SRMR = .038). This model included fathers’ depression, siblings’ perception of communication quality with fathers, and father-reported disorder severity and family social support (see Table 3). In this model, siblings’ reporting of better quality of life was significantly associated with their perception of better communication with fathers (path F: p = .001), with fathers’ reporting lower depression (path C: p<.001), and sibling being younger (B = −1.637, SE = .404, p<.001, 95% CI [−2.429, −.845]). Thus, support was found for paths C and F in the conceptual model.

Table 3.

Results with sibling outcomes as dependent variables and predictor variables reported by father and siblings.

	Quality of life			Mental health			Adjustment to the disorder			Prosocial behavior
	B	SE	95% CI	B	SE	95% CI	B	SE	95% CI	B	SE	95% CI
Model pathways
Direct pathways
DBC-P ->Sibling outcome (A)	−.13	.48	[−1.07, .81]	.02	.21	[−.39, .45]	.02	.02	[−.02, .06]	.05	.05	[−.05, .15]
DBC-P ->SCL-90-Rdep (B)	.07	.06	[−.04, .19]	.06	.06	[−.04, .18]	.08	.06	[−.03, .20]	.07	.06	[−.04, .19]
SCL-90-Rdep ->Sibling outcome (C)	−6.98	1.87	[−10.64, −3.31]	2.62	.85	[.96, 4.28]	.11	.08	[−.05, .27]	.07	.20	[.33, .48]
FSS ->SCL-90-Rdep	−.01	1.86	[−.03, .01]	−.01	.01	[−.03, .01]	−.00	.01	[−.03, .01]	−.00	.01	[−.03, .01]
DBC-P*FSS ->SCL-90-Rdep (D)	−.00	.00	[−.01, .01]	−.00	.00	[−.01, .01]	−.00	.00	[−.01, .01]	−.00	.00	[−.01, .01]
SCL-90-Rdep ->PCCS (E)	.38	1.08	[−1.74, 2.51]	−.02	1.09	[−2.17, 2.11]	−.05	1.11	[−2.23, 2.12]	−.18	1.12	[−2.38, 2.01]
PCCS ->Sibling outcome (F)	.47	.14	[.20, .74]	−.08	.06	[−.021, .03]	.00	.00	[−.01, .01]	.06	.02	[.03, .09]
Indirect pathways
Path (E)*Path (F)a	.18	.52	[−.84, 1.20]	.00	.09	[−.18, .18]	−1.21	.00	[−.00, .00]	−.01	.07	[−.14, .12]
Path (B)*Path (E)*Path (F)b	.01	.04	[−.06, .09]	.00	.00	[−.01, .01]	−1.00	3.68	[−7.33, 7.12]	−.00	.00	[−.01, .00]
Path (B)*Path (C)c	−.50	.44	[−1.36, .36]	.18	.16	[−.14, .51]	.00	.01	[−.01, .02]	.00	.01	[−.02, .03]

Note. Capital letters in parenthesis (A, B, C, D, E, F) refer to model pathways.

^aIndirect effect of parental mental health via parent–child communication.

^bIndirect effect of disorder severity via parental mental and parent–child communication.

^cIndirect effect of disorder severity via parental mental health. DBC-P=Developmental Behavior Checklist Primary Carer Version; SCL-90-Rdep=Symptom Checklist-90-Revised Depression Symptoms Subscale; FSS=Family Support Scale; PCCS=Parent Child Communication Scale. Significant pathways (p < .05) are bolded.

Table 4.

Results with sibling outcomes as dependent variables and predictor variables reported by mother and siblings.

	Siblings’ quality of life			Siblings’ mental health			Siblings’ adjustment to the disorder			Siblings’ prosocial behavior
	B	SE	95% CI	B	SE	95% CI	B	SE	95% CI	B	SE	95% CI
Model pathways
Direct pathways
DBC-P ->Sibling outcome (A)	−.11	.36	[−.82, .60]	.09	.16	[−.23, .42]	.00	.01	[−.02, .03]	.03	.04	[−.04, .11]
DBC-P ->SCL-90-Rdep (B)	.02	.05	[−.07, .12]	.02	.05	[−.07, .12]	.02	.05	[−.07, .12]	.02	.05	[−.07, .12]
SCL-90-Rdep ->Sibling outcome (C)	−.42	1.24	[−2.86, 2.00]	−.17	.55	[−1.26, .91]	−.05	.05	[−.16, .05]	−.05	.13	[−.31, .21]
FSS ->SCL-90-Rdep	−.02	.01	[−.05, .00]	−.02	.01	[−.05, .00]	−.02	.01	[−.05, .00]	−.02	.01	[−.05, .00]
DBC-P*FSS ->SCL-90-Rdep (D)	.00	.00	[−.00, .01]	.00	.00	[−.00, .01]	.00	.00	[−.00, .01]	.00	.00	[−.00, .01]
SCL-90-Rdep ->PCCS (E)	.16	.57	[−.96, 1.29]	.18	.57	[−.95, 1.31]	.19	.57	[−.93, 1.32]	.13	.57	[−.99, 1.26]
PCCS ->Sibling outcome (F)	.44	.15	[.14, .74]	−.07	.07	[−.21, .06]	−.00	.00	[−.01, .01]	.07	.01	[.04, .11]
Indirect pathways
Path (E)*Path (F)a	.07	.26	[−.43, .58]	−.01	.04	[−.09, .07]	−.00	.00	[−.00, .00]	.01	.04	[−.07, .10]
Path (B)*Path (E)*Path (F)b	.00	.00	[−.01, .01]	−.00	.00	[−.00, .00]	−7.95	4.41	[−9.44, 7.85]	.00	.00	[−.01, .00]
Path (B)*Path (C)c	−.01	.03	[−.08, .06]	−.00	.01	[−.03, .02]	−.00	.00	[−.00, .00]	−.00	.00	[−.01, .00]

Note. Capital letters in parenthesis (A, B, C, D, E, F) refer to model pathways.

^aIndirect effect of parental mental health via parent–child communication,.

^bIndrect effect of disorder severity via parental mental and parent–child communication.

^cIndirect effect of disorder severity via parental mental health. DBC-P=Developmental Behavior Checklist Primary Carer Version; SCL-90-Rdep=Symptom Checklist-90-Revised Depression Symptoms Subscale; FSS=Family Support Scale; PCCS=Parent Child Communication Scale. Significant pathways (p < .05) are bolded.

The model with mother-reported variables as predictors of sibling-reported quality of life showed good model fit (χ² (14 df)=9.33, p = .86, CFI = 1.000, TLI = 1.025, RMSEA=.000, 90% CI [.000, .036], SRMR=.033). This model included mothers’ depression, siblings’ perception of communication quality with mothers and mother-reported disorder severity and family social support (see Table 4). In this model, siblings’ reporting of better quality of life was significantly associated with their perception of better communication with their mothers (path F: p=.003), sibling being younger (B = −1.632, SE=.405, p<.001, 95% CI [−2.425, −.839]), sibling being a boy (B = −3.381, SE = 1.652, p=.041, 95% CI [−6.619, −.143]), and having a mother with lower education level (B = −3.412, SE = 1.013, p=.001, 95% CI [−5.398, −1.426]). Thus, support was found only for path F in the conceptual model.

Siblings’ mental health

The model with father-reported predictors of sibling-reported mental health showed good model fit (CFI=.998, TLI=.995, RMSEA=.012, 90% CI [.000, .059], SRMR=.034). This model included fathers’ depression, siblings’ perception of communication quality with fathers, and father-reported disorder severity and family social support. In this model, paternal depression was significantly associated with siblings’ mental health problems (path C: p=.002). No other effects, direct, indirect, or interactive were significant. Thus, support was found only for path C in the conceptual model.

The model with mother-reported predictors of sibling-reported mental health showed good model fit (χ² (14 df)=11.82, p = .621, CFI = 1.000, TLI = 1.012, RMSEA=.000, 90% CI [.000, .049], SRMR=.036). This model included mothers’ depression, siblings’ perception of communication quality with mothers, and mother-reported disorder severity and family social support. In this model, there were no significant effects. Thus, no support was found for any of the paths in the conceptual model.

Siblings’ adjustment to the CD

The model with father-reported predictors of sibling-reported adjustment to the CD showed good model fit (χ²(14 df)=12.27, p = .585, CFI = 1.000, TLI = 1.015, RMSEA<.001, 90% CI [.000, .050], SRMR=.032). This model included fathers’ depression, siblings’ perception of communication quality with fathers, and father-reported disorder severity and family social support. In this model, there were no significant effects. Thus, no support was found for any of the paths in the conceptual model.

The model with mother-reported predictors of sibling-reported adjustment to the CD showed good model fit (χ² (14 df)=9.86, p = .772, CFI = 1.000, TLI = 1.023, RMSEA=.00, 90% CI [.000, .039], SRMR=.032). This model included mothers’ depression, siblings’ perception of communication quality with mothers, and mother-reported disorder severity and family social support. In this model, there were no significant effects. Thus, no support was found for any of the paths in the conceptual model.

Siblings’ prosocial behavior

The model with father-reported predictors of sibling-reported prosocial behavior showed good model fit (χ²(14 df)=15.96, p = .316, CFI=.994, TLI=.984, RMSEA=.022, 90% CI [.000, .063], SRMR=.038). This model included fathers’ depression, siblings’ perception of communication quality with fathers, and father-reported disorder severity and family social support. In this model, siblings’ prosocial behavior was significantly associated with siblings’ perception of better communication quality with fathers (path F: p<.001) and sibling being a girl (p=.047). Thus, support was found only for path F in the conceptual model.

The model with mother-reported predictors of sibling-reported prosocial behavior showed good model fit (χ²(14 df)=11.88, p = .616, CFI = 1.000, TLI = 1.011, RMSEA=.00, 90% CI [.000, .049], SRMR=.037). This model included mothers’ depression, siblings’ perception of communication quality with mothers, and mother-reported disorder severity and family social support. In this model, siblings’ prosocial behavior was significantly associated with siblings’ perception of better communication quality with mothers (p<.001). Thus, support was found only for path F in the conceptual model. See Figure S1 for an overview of the significant findings.

Discussion

We empirically tested a family system model aiming to capture siblings’ own perspectives on their psychosocial adjustment and experiences of communication with their parents. We relied on parents for information about CD severity, parental depressive symptoms, and family social support. With this cross-informant design, our study provides important knowledge about factors associated with siblings’ psychosocial adjustment. In terms of significant associations, better parent–sibling communication (path F) was significantly associated with positive sibling outcomes, namely quality of life and prosocial behavior. Fathers’ depressive symptoms (but not mothers’) were a significant predictor of sibling-reported quality of life and mental health (path C). We did not find support for the other pathways proposed by our conceptual model.

In the model, CD severity was proposed as a significant stressor for both parental depression and sibling psychosocial adjustment, but no evidence was found for these relationships. Previous studies show strong associations between CD severity and parent mental health (Scherer et al., 2019), as well as CD severity and sibling mental health problems, both for chronic medical and neurodevelopmental disorders (Vermaes et al., 2012; Wolff et al., 2022). The lack of significant results for these associations in the tested model may be an artifact of the complexity of the model and the inclusion of several indirect effects. It may also be related to characteristics of the sample, comprising primarily parents with high socioeconomic status and educational background. Limited variation within the sample may have made this association difficult to capture as these families may have more family-related resources such as access to more illness information and less strained communication (Vatne et al., 2015). Moreover, although inclusion criteria were initially based on a cross-disorder understanding of sibling risk, the final sample comprised primarily families of children with neurodevelopmental disorders, which may be considered less acute compared to medical disorders such as cancer or heart diseases and thus, made it more difficult to detect effects of certain aspects of CD severity, such as functional impairments. Studies have found greater general parenting stress to be associated with greater parental responsibility for treatment management and unrelated to illness duration and severity (Cousino & Hazen, 2013). This may reflect that there is an important difference between disorder severity and the load of treatment management on parents, ultimately effecting sibling psychosocial adjustment across CDs more. Alternatively, our results may suggest that siblings of children with less acute disorders, such as neurodevelopmental conditions, are less affected by the disorder itself, as long as they experience open and emotionally supportive communication with their parents, and as long as their fathers do not have mental health problems. Several previous studies have found that CD severity does not predict sibling psychosocial adjustment in a vacuum (Vermaes et al., 2012; Wolff et al., 2022) highlighting the need for a broader understanding of stressors within the family context, and the factors that might interact with disorder severity to impact sibling psychosocial adjustment.

Interestingly, father-reported depression was related to siblings experiencing lower quality of life and mental health, whereas mother-reported depression was not. Some previous research has also found siblings’ self-reported psychosocial adjustment to be more aligned with father-report than mother-report (Fredriksen et al., 2023). A possible explanation for these results is that mothers provide more care to the child with a CD than fathers (Meadan et al., 2015), potentially placing greater responsibility for siblings on fathers. This may, in turn, make fathers more attuned to siblings’ well-being, which may explain why siblings are more affected when fathers have mental health problems. Hence, paternal mental health problems may affect siblings more than maternal mental health problems. Alternatively, although the burden of having a child with a CD seems to affect mothers more than fathers (Pinquart, 2018), and maternal depression may be especially important in sibling psychosocial adjustment in families with a child with autism (Tudor et al., 2018), higher parental mental health problems have been found to be related to higher informant discrepancies about sibling mental health (Rankin et al., 2017). This may support the interpretation that fathers are more tuned in with sibling needs then mothers. Mothers are more often informants than fathers in research (Rankin et al., 2019), but our findings underscore the importance of including father reports in sibling research and suggest that sibling psychosocial adjustment may be influenced by the specific and interconnected roles and responsibilities (i.e., subsystems) within the family system.

Siblings experiencing a better quality of communication with their fathers and mothers also reported experiencing better quality of life and more prosocial behavior but did not report having less mental health difficulties or CD-related adjustment problems. It is interesting that communication was related to positive domains but not negative domains. Experiencing better communication with parents may not directly reduce symptoms of mental health problems. However, it may facilitate a better understanding of the CD, promoting prosocial behavior, and siblings may in turn seek more emotional support from their parents (Haukeland et al., 2015; Incledon et al., 2015; Murphy et al., 2017). Notably, there were some age and gender differences in our results, with younger siblings reporting higher quality of life across the mother and father models, and girls reporting significantly more prosocial behavior than boys (significant only in the father model). The results highlight the importance of including a broad range of sibling outcomes as measures of sibling psychosocial adjustment and to consider that siblings of different ages and genders may have different experiences. However, the age and gender differences may just be reflective of general developmental processes, not specifically related to the sibling experience. Girls are often reported to display more prosocial behavior than boys (Ferschmann et al., 2024), and well-being and mental health are generally worsening in adolescence compared to childhood (Morken et al., 2021).

We examined family social support as a potential protective factor and found no evidence that family social support moderated the relationship between CD severity and parental depression. This contrasts with past research linking lack of social support to depression and stress (Kendler et al., 2002), and the strong theoretical arguments to include social support in our family model (Uchino, 2009; Watson, 2012). Tudor et al. (2018) similarly found that family social support did not predict familial or maternal functioning. They propose that measures that capture specific aspects of social support such as feelings of being understood and the opportunity to talk about problems may be more appropriate for families of children with CDs (e.g., Boyd, 2002). The social support measure we used, the FSS, may not capture such specific aspects of social support. While both social support and family system resources, such as communication quality, can facilitate adaptation to living with a child with a CD, it is possible that these two factors promote adaptation in different ways. For example, communication quality may affect adaptation more directly (Murphy et al., 2017), whereas social support may act as an indirect buffer in reducing more acute parental stress (Boyd, 2002). Hence, whereas sibling-perceived social support may be an important factor for siblings of children with neurodevelopmental disorders and their psychosocial adjustment (Kirchhofer et al., 2022), parent-perceived social support and its buffering effect for the sibling (e.g., moderating effect) may not be straightforward and a more nuanced analysis of how different kinds of sources of support are perceived and utilized within families may be required.

The lack of any significant associations in the models with CD-related adjustment problems (i.e., negative adjustment) as outcome may question the validity of the NAS as an outcome of the sibling experience. Recently, Veerman et al. (2025) suggested that the CD-related adjustment measured by the NAS is a process rather than an outcome. That is, CD-related adjustment as measured by the NAS taps the process in which siblings appraise and adapt to the sibling situation. This process contributes to, but is not necessarily part of, psychosocial adjustment. In future revisions of our model, it should be considered whether CD-related adjustment could be an intermediate variable, for example as a potential mediator between disorder severity and siblings’ psychosocial adjustment. However, it is important to note that no evidence was found for an association between disorder severity and CD-related adjustment problems in the current study. Thus, it may be that the CD-related adjustment process measured by the NAS is an intrapersonal process, largely unaffected by the larger family system. In the future, it would be interesting to dive deeper into the factors that may affect CD-related adjustment in siblings and examine its relationship with sibling relationship quality.

Implications

The current study has several implications. The first is that paternal mental health should be carefully considered in families of children with CDs, as it may be critical to sibling psychosocial adjustment. A broad family-oriented approach to sibling assessment, including sibling self-report and reports from both parents, may be useful to best capture sibling and family needs. A further implication is that improving parent–sibling communication quality may promote siblings’ psychosocial adjustment. A recent review of 24 sibling intervention studies found promising improvements in siblings’ emotional and behavioral adjustment, though evidence remains mixed (Wolff et al., 2023b). Interventions typically focused on psychoeducation, coping skills, and stress reduction, with limited parent involvement. Notably, none of the reviewed programs addressed parent–sibling communication directly, despite its documented importance in families of children with chronic disorders (Murphy et al., 2017) and so this area of intervention remains unexplored. It is also possible that interventions aiming to improve paternal mental health may have the added benefit of improving sibling quality of life—or indeed the other way around. However, research has found it difficult to improve children’s quality of life by improving parent mental health alone which may reflect the need for a sibling-specific intervention approach (Wakefield et al., 2021).

For future research, we suggest exploring alternative ways to understand and measure disorder severity and social support, as there may be important nuances to these concepts that provide different findings. Moreover, parent mental health could be explored beyond depression symptoms, as other aspects of parent mental health and parental stress may affect sibling psychosocial adjustment in different ways (Pinquart, 2018). Moreover, including a measure of time since diagnosis and of sibling relationship quality could provide interesting information as it may be relevant for sibling psychosocial adjustment. Finally, testing our conceptual model on a different sample, such as a subcategory of neurodevelopmental disorders or exclusively acute medical disorders may provide further nuances.

Limitations

While SEM models can be powerful tools for examining mediation and moderation, applying them to cross-sectional data can pose significant limitations. These limitations are primarily related to difficulties in establishing causality, temporal sequence, and the risk of reverse causality (Cole & Maxwell, 2003). Longitudinal data or experimental designs are typically preferred when testing mediation and moderation processes to capture the dynamic nature of these relationships more accurately. However, while mediation is most often used as a way to demonstrate a causal pathway through which a predictor can change an outcome, it can also be used as a means of exploring possible explanations of association (Fairchild & McDaniel, 2017). In identifying possible explanations, we can inform future work that more clearly incorporates temporal precedence of predictor to mediator and mediator to outcome. It is also important to note that according to the Hyman-Tate criterion (Tate, 2015), establishing mediation is not so much about actual temporal sequence as conceptual temporal sequence. If we had proposed stable personal dispositions (e.g., sibling personality traits) as intermediate variables, this would have been problematic no matter the temporal sequence of our measurements, because it is unlikely that stable personal dispositions in siblings are affected by their parents’ current state of mind (e.g., depressive symptoms). As such, we argue that the proposed temporal sequence of our variables is conceptually justified, and that the mediating variables proposed in our model (i.e., parental depression and parent–sibling communication) are state-dependent, likely to change over time, and malleable through intervention. Thus, making them suitable for testing mediation effects in a cross-sectional design.

The open recruitment method of our study may have introduced response bias, as families who chose to participate may differ in significant ways from those who did not (i.e., perhaps relatively high functioning, motivated, and self-organized sample). The sample is predominantly composed of families of higher socioeconomic status and with a relatively homogenous ethnic and cultural background, which may raise concerns about the representativeness of the findings and their generalizability to more diverse populations and should be considered when interpreting the findings. Future studies should strive to include more diverse samples. The recruitment process, relying on healthcare services, user organizations, and various advertisements, introduces potential bias, as we cannot confirm equal exposure to recruitment efforts across all eligible CDs, potentially limiting sample representativeness. Another potential limitation is that we had limited control over how independently the children completed the questionnaires.

In this study, depressive symptoms served as the proxy for parent mental health as maternal depression served as a key pathway in sibling adjustment in the model that inspired this study (Tudor et al., 2018). Moreover, systematic and meta-analysis have found depression symptoms as one of two major mental health-related outcomes in parents of children with CDs (Cohn et al., 2020). Although there are undoubtedly many ways in which parents are affected, including anxiety and posttraumatic stress symptoms (Carmassi et al., 2021; Cohn et al., 2020), using a global mental health measure would potentially be less specific than depressive symptoms and may be more trait dependent as it would include more stable dispositions such as interpersonal sensitivity, thought problems, and attention-deficit (Derogatis & Unger, 2010). Hence, using the Global Symptom Index of the SCL90 would not have been in line with our proposal that aspects of parental mental health could serve as a mediator between disorder severity and sibling psychosocial adjustment. Furthermore, using a global mental health measure would have vaguer implications, as these stable dispositions are less likely to be influenced by having a child with a CD and thus, are less relevant to target in family-centered care.

Conclusions

Our findings highlight the complex interplay of factors within the family system that influences sibling psychosocial adjustment, which resonates with the applied systemic theories (Minuchin, 2018; Watson, 2012), yet highlights the difficulty of finding empirical support for these complex models. Nevertheless, similarly to previous research (Tudor et al., 2018), our study supports the usefulness of structural equation modeling for theory testing in sibling research. Our results underscore the importance of examining the interconnected roles within the family, the differential impact of parental mental health (mothers vs. fathers) on siblings, the importance of communication quality for positive aspects of sibling psychosocial adjustment, and the need for comprehensive, multi-informant approaches in sibling research and interventions. As such, our study provides the field with a further step toward an empirically based, and theoretically driven understanding of sibling psychosocial adjustment.

Supplementary material

Supplementary material is available online at Journal of Pediatric Psychology (https://academic.oup.com/jpepsy/).

Author contributions

Solveig Kirchhofer (Writing original draft [lead], Writing - review and editing [lead], Conceptualization [equal], Data curation [lead], Project administration [equal], Visualization [lead]), Stian Orm (Writing - review and editing [supporting], Conceptualization [equal], Data curation [equal], Methodology [equal]), Nancy Briggs (Data curation [equal], Formal analysis [lead], Methodology [equal], Software [lead], Supervision [equal], Writing - review and editing [supporting]), Trude Fredriksen (Data curation [equal], Resources [supporting], Writing - review and editing [supporting]), Erica Zahl (Conceptualization [supporting], Data curation [supporting], Writing - review and editing [supporting]), Caitlin Prentice (Data curation [supporting], Writing - review and editing [supporting]), Matteo Botta (Data curation [lead], Writing - review and editing [supporting]), Lauren Kelada (Supervision [supporting], Writing - review and editing [supporting]), Ursula M. Sansom-Daly (Supervision [supporting], Writing - review and editing [supporting]), Torun Marie Vatne (Project administration [equal], Supervision [supporting], Writing - review and editing [supporting]), and Krister Fjermestad (Conceptualization [lead], Data curation [equal], Funding acquisition [lead], Project administration [lead], Supervision [lead], Writing - review and editing [supporting])

Funding

This work was supported by the Norwegian Research Council (321027), to (K.W.F.) Lillestrøm municipality.

Conflicts of interest: None declared.