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. 2018 Apr 20;41:91–100. doi: 10.1007/8904_2018_105

Parenting a Child with Phenylketonuria: An Investigation into the Factors That Contribute to Parental Distress

Olivia Ambler 13, Emma Medford 14, Dougal J Hare 13,✉
PMCID: PMC6122051  PMID: 29675588

Abstract

Phenylketonuria (PKU) is an inherited metabolic condition that can lead to the onset of intellectual disabilities if not strictly managed through a low-protein diet. Parents are responsible for supervising their child’s treatment for PKU, which may impact on their experience of distress. This cross-sectional study aimed to identify the factors that contribute to distress in parents who care for a child with PKU, distinct from parents in the general population. Thirty-eight parents of children and adolescents with PKU and 32 parents in the general population completed the questionnaires measuring parental psychological resilience, child behaviour problems, perceived social support and distress. Parents of children with PKU also completed measures of their child’s care dependency and behaviour related to developmental and intellectual disabilities. The findings revealed no statistically significant differences in distress between the groups, but parents of children with PKU reported more child behaviour problems. Multiple regression analysis identified that parental psychological resilience and child anxious behaviour explained 35% of the variance in distress for parents of children with PKU. By comparison, parental psychological resilience and generic child behaviour only accounted for 19% of the variance in distress for parents in the general population. This has implications for developing interventions in clinical settings that aim to reduce parents’ distress by enhancing their psychological resilience and supporting them to manage child behaviour difficulties, particularly anxious behaviour. Future research should include larger, more diverse samples and use longitudinal study designs.

Keywords: Behaviour, Distress, Parents, Phenylketonuria, Resilience

Introduction

Phenylketonuria (PKU) is an inherited metabolic condition that can lead to the development of intellectual disabilities if not strictly managed through a low-Phe diet (Cleary 2015). Parents are responsible for supervising the diet during their offspring’s childhood and adolescence, which is likely to cause them distress (Blau et al. 2010).

Research into the well-being of parents of children with PKU has yielded mixed findings. Some studies indicate higher levels of depression and anxiety compared to the general population (Mahmoudi-Gharaei et al. 2011). Other studies suggest that well-being is comparable to that observed in non-PKU reference groups (Kazak et al. 1988), and in some cases, superior to families with other biochemical disorders (Ten Hoedt et al. 2011a, b). A large-scale international study found similar quality of life scores to parents in the general population, but parents of children with PKU reported a high emotional impact of the condition, anxiety around blood Phe concentrations and guilt if the diet was not adhered to (Bosch et al. 2015).

In order to support parents with the specific challenges of caring for a child with PKU, it is necessary to understand the factors that contribute to distress. Previous research suggests that psychological resilience and social networks are important protective factors for parents’ well-being (Lord et al. 2005, 2008). Moreover, child adaptive functioning, satisfaction with social support and difficulty meeting the child’s health care needs are shown to predict parenting stress (Waisbren et al. 2004). However, a recent study found social support and child dependency did not significantly predict parents’ distress, but psychological resilience did (Medford et al. 2017a). Given these inconsistent findings, further research is needed to better understand the impact of child dependency, social support, psychological resilience and distress experienced by parents of children with PKU.

Another factor that could affect parents’ distress is the presence of child behaviour problems (Craig et al. 2016). Research with parents of young people with type 2 diabetes highlights child behaviour impacts on parents’ distress, particularly when this interferes with diabetes management (Hilliard et al. 2010). Similarly, fewer child behaviour problems predicted well-being in a study with parents of children with non-progressive neurodevelopmental disorders (King et al. 1999). These findings have implications for investigating distress experienced by parents of children with PKU. Children with PKU are reported to present 1.5–1.9 times the rate of behaviour problems observed in the general population (Smith and Knowles 2000). High rates of internalising problems (Jahja et al. 2013), impulsive behaviour (Christ et al. 2006) and reduced social competence are reported in this group (Brumm et al. 2010). This could be due to elevated Phe levels, which have been linked to a reduction in the concentration of neurotransmitters involved in mood regulation and executive functioning (Kolb and Whishaw 2003). Other studies report more internalising problems for adolescents with good dietary adherence, indicating that the restrictive nature of the diet itself could impact on behaviour (Cappelletti et al. 2013). However, to date, there has been a scarcity of research into the impact of child behaviour on parents’ distress.

In order to address this paucity of research, the current study was planned as part of a wider programme of research looking at families of children with PKU and which was undertaken in the north west of England. The first study by Medford et al. (2017a) examined stress, resilience and social support in parents of children with PKU and the relationship of these factors to both child dependency and treatment compliance [proportion of blood Phe concentrations within target range in previous year], with the choice of factors to be investigated being based on an accompanying systematic review (Medford et al. 2017b). The second study by Carpenter et al. (2018) was conducted in parallel with Medford et al.’s study and reported and analysed the lived experiences of parents of children with PKU under 2 years of age. The current study aimed to compliment and build upon this work by focusing on the relationship between parental stress and reported child behaviour, a relationship that has been examined in the case of many other forms of developmental disorder such as autistic spectrum disorder (Hall and Graff 2012) and diabetes (Hilliard et al. 2010).

It was hypothesised in the current study that parents of children with PKU would report higher levels of distress and a higher incidence of child behaviour problems than those in the general population and that child behaviour problems and psychological resilience would predict distress in parents of children with PKU.

Method

Participants

Phenylketonuria Group

Parents of children and adolescents were invited to participate in the study if their child was between 0 and 18 years old and had a formal diagnosis of PKU.

Reference Group

Parents of children and adolescents were invited to participate if their child was between 0 and 18 years old and did not have a diagnosis of PKU, or any other physical health condition.

Exclusion criteria were any other significant caring responsibilities, or physical and/or mental health problems that could impact on distress levels for parents in both groups.

Measures

Demographic Information

A demographic questionnaire (Medford et al. 2017a) was used to obtain information including parent age, child age, average family income and highest qualification.

Psychological Distress

The General Health Questionnaire (GHQ-12) was used to measure psychological distress (Goldberg and Williams 1988). The scale has 12 items; scores are summed across the items to provide a total score for distress. Higher scores indicate a greater severity of distress (anxiety and depression), with scores above 12 within the clinical range (Goldberg et al. 1997). The GHQ-12 has good psychometric properties and is validated within the UK (Hankins 2008).

Psychological Resilience

The Resilience Scale for Adults (RSA) is a self-report measure of psychological resilience. Resilience refers to ‘positive resources that may be activated in the context of stress to prevent the development of negative mental health outcomes’ (Morote et al. 2017). The RSA has 33 items and 6 subscales: perception of self, planned future, social competency, structured style, family cohesion and social resources. Scores are summed across these subscales to provide a total score for resilience, with higher scores indicating higher levels of resilience. In a recent review of measures of psychological resilience (Windle et al. 2011), the RSA was scored high for reliability and validity, and high internal consistency scores are reported with samples recruited within the UK (Medford et al. 2017a).

Perceived Social Support

Perceived social support has been defined as the experience of being cared for, valued and respected by others (Roohafza et al. 2014). The Multidimensional Scale of Perceived Social Support (MSPSS) was used to measure the levels of perceived social support (Zimet et al. 1988). This scale has 12 items and three subscales (significant other, friends and family), which are scored using a 1–7 point Likert scale. A total score can also be calculated by summing subscales scores. Good internal consistency scores are reported for this measure with samples recruited within the UK (Medford et al. 2017a).

Child Behaviour

The Eyberg Child Behavior Inventory (ECBI) is a parent-report questionnaire measuring disruptive behaviours in children ages 2–16 (Eyberg and Ross 1978). The ECBI has 36 items and 2 subscales: an intensity scale to measure the frequency of behaviour problems and a problem scale to assess whether parents perceive their child’s behaviour as a problem. The subscale item scores are summed to provide a total score for behaviour intensity and behaviour problems. All item scores are summed to provide a total score for child behaviour. Higher scores indicate higher levels of behaviour problems, with a cut-off score of 131 for disruptive behaviour on the intensity scale and 15 on the problem scale. High internal consistency scores are reported for this measure, which has been validated with the US, Swedish, Spanish and Norwegian samples (Weeland et al. 2017).

The Developmental Behaviour Checklist Parent/Carer Version (DBC) was used to assess behaviour related to developmental disorders in families affected by PKU. This questionnaire measures the incidence of child behaviour and emotional problems over a 6-month period, for children aged 4–18 (Einfeld and Tonge 1995). There are 96 items and 5 subscales: disruptive/antisocial; self-absorbed; communication disturbance; anxiety and social relating. Item scores are summed across each subscale to provide a measure of that behaviour domain. A total score is calculated by summing all of the subscale scores, with a clinical cut-off of 46 for behaviour related to developmental disabilities. The questionnaire has demonstrated good internal consistencies and has been validated with Australian samples (Einfeld and Tonge 2002).

Child Dependency

A child dependency questionnaire was developed by Medford et al. (2017a) to measure how much a child depends on their caregiver to adhere to a low-protein diet. Scores on this questionnaire range from 1 to 7, with higher scores indicating higher levels of the child’s care dependency.

Procedure

Recruitment

To recruit parents of children with PKU, an advert for the study was posted on the National Society for Phenylketonuria (NSPKU) website, newsletter and online social media sites (Twitter and Facebook). The NSPKU is a UK-based third sector organisation that provides support to parents, professionals and adults affected by PKU. The researcher (OA) also attended two NSPKU conferences and a community event to raise awareness of the study. Study adverts were displayed on the Cardiff University premises to recruit parents in the general population. Potential participants were encouraged to contact the researcher using the email address displayed on study adverts.

All eligible parents were posted a questionnaire pack containing the research questionnaires, participant information sheets and a consent form. For parents in the general population, questionnaires included the GHQ-12, RSA, MSPSS and the ECBI. Parents of children with PKU were asked to complete the same questionnaires as those in the general population, with the addition of the DBC and the child dependency questionnaire. All parents were provided with a pre-stamped envelope to return the completed questionnaires and consent forms to the researcher. An opt-out form was also provided for parents to fill in and return if they no longer wished to participate in the study. An additional questionnaire pack was sent with a reminder letter if the initial questionnaire pack was not responded to.

Once data collection was complete, all parents were entered into a prize draw to win a £100 shopping voucher.

Approval for the study was gained from Cardiff University School of Psychology Ethics Committee.

Statistical Analysis

Scores were non-normally distributed for all parent-report measures in the PKU group except for ECBI intensity subscale and RSA total score, which were normally distributed. Subscale scores for the MSPSS and the child dependency scale were positively skewed. Scores on all subscales of the DBC were negatively skewed, as were scores for the GHQ-12 and the ECBI problem subscale.

In the reference group, all scores were non-normally distributed except for the ECBI intensity subscale, the RSA and the GHQ-12, which were normally distributed. Subscales of the MSPSS were all positively skewed and scores on the ECBI problem subscale were negatively skewed.

Due to the high number of non-normally distributed variables and the small sample sizes, bootstrapping approaches were used to provide a non-parametric alternative for t-tests, Pearson’s correlations and multiple regressions. This process was selected due to its higher statistical power than other approaches, particularly for studies with small sample sizes (Field 2013). A bias-corrected and accelerated or BCa method was calculated based on 1,000 bootstrapped samples. This method is reported to produce more accurate confidence intervals than the percentile method (Field 2013).

An independent samples t-test was used to compare levels of distress, as measured by scores on the GHQ-12, and child behaviour problems, as measured by scores on the ECBI problem and intensity subscales, between the groups. Pearson’s correlations were used to measure the association between variables. Bonferroni corrections were not used based on studies suggesting that these can increase type 2 error to unacceptable levels in studies with small samples (Bland and Altman 1996; Nakagawa 2004).

A multiple regression analysis was selected to examine the predictors of psychological distress, as measured by scores on the GHQ-12. Predictor variables were selected based on statistically significant bivariate correlations with GHQ-12 scores.

All data analysis was carried out using IBM SPSS Statistics 20 software package, with the p value set at 0.05.

Results

Participants

Phenylketonuria l Group

Forty-nine parents contacted the researcher regarding taking part in the study. Four parents responded to the NSPKU website advert, 18 responded to adverts posted on social media sites and 27 following the NSPKU conferences and community event. Forty parents returned completed forms and questionnaires, with two parents opting out. Therefore, 38 eligible parents were included, representing a 78% participation rate. Thirty-four children met the age criteria for the ECBI and 28 for the DBC. Three participants had missing responses on the RSA (1–3 items) and one participant had a missing response on the GHQ-12 (1 item). Missing answers were scored using the participant’s average score for that measure.

Six fathers and 32 mothers were represented. Four parents did not state their household income; the mean value for the remaining 34 parents was £56,029.41 (range = £10,000–150,000, SD = 32,976.33) and parents’ mean age was 40 years and 6 months (range = 25–59, SD = 8.12). Parents reported a range of qualifications: 5 (14%) had a Master’s degree; 17 (46%) had Undergraduate degrees; 2 (5%) had Doctorates; 4 (11%) had Diplomas; 8 (22%) had GCSE’s; 1 had A-levels (3%) and 1 parent did not state their highest qualification. Child mean age was 8 years and 1 month (range 1–17 years, SD = 5.36). Twenty one (55%) of the children were female and 17 (45%) were male. The majority of families lived in the UK, with 30 (76%) from England and Wales (79%), 3 (8%) from Northern Ireland, 1 (3%) from the Republic of Ireland, 3 (8%) from Scotland and 1 family from New Zealand (3%).

Non-Phenylketonuria Reference Group

Fifty-six parents contacted the researcher about taking part in the research in response to the study adverts. Thirty-two parents returned completed questionnaires, representing a 57% participation rate. All children met the age criteria for the ECBI. Thirty families met the age criteria for the ECBI. One participant had a missing response on the GHQ-12, which was scored using their average score for this measure.

The sample represented 8 (25%) fathers and 24 (75%) mothers. The mean parent age was 38 years (range = 27–54, SD = 7.12) and the mean child age was 5 years and 6 months (range = 3 months–14 years, SD = 3.85). Eighteen (56%) of the children were male and 14 (44%) were female. Two parents did not state their average income but the mean household income for the remaining 29 parents was £73,333.33 (range = £18,000–150,000, SD = 33,777.50). A range of qualifications were represented: 22 (69%) parents reported Undergraduate degrees; 6 (19%) had Master’s degrees; 2 (6%) reported Diplomas; 1 (3%) had A-levels and 1 (3%) had GCSE’s. Nineteen of the parents lived in Wales (59%) and 13 lived in England (41%). English was the first language for all parents in both groups.

Descriptive Statistics for Scores on Parent-Report Measures

Mean scores for distress were comparable across the two groups (see Table 1), with nine parents scoring above the cut-off for distress in the PKU group and six in the reference group. Scores on measures of resilience and social support were lower for parents of children with PKU compared to those in the general population. Parents of children with PKU also reported more child behaviour problems, with six parents scoring above the threshold on the ECBI intensity subscale and five on the problem subscale. By comparison, three parents from the general population scored above the threshold on the problems subscale of the ECBI. The incidence of behaviour related to developmental disorders was reported as low, with three parents scoring above the clinical cut-off for behaviour related to developmental and intellectual disabilities.

Table 1.

Descriptive statistics for parent-report measures for participants of PKU group (Group 1) and Reference group (Group 2)

Measure Group N Mean (SD) Range (scale range)
GHQ-12 1 38 10.29 (2.96) 4–18 (0–36)
RSA 2 32 9.63 (3.66) 1–17 (0–36)
1 38 179.32 (24.00) 123–216 (33–231)
MSPSS friend 2 32 191.06 (20.15) 135–220 (33–231)
1 38 21.39 (6.34) 5–28 (4–28)
MSPSS family 2 32 24.16 (6.00) 4–28 (4–28)
1 38 22.26 (5.57) 4–28 (4–28)
MSPSS sig. other 2 32 23.38 (5.75) 4–28 (4–28)
1 38 24.18 (5.62) 4–28 (4–28)
MSPSS total 2 32 24.66 (6.42) 4–28 (4–28)
1 38 67.84 (14.08) 16–84 (12–84)
ECBI intensity 2 32 72.16 (17.39) 12–84 (12–84)
1 34 103.56 (31.03) 42–168 (38–266)
ECBI problem 2 30 88.63 (21.48) 48–126 (38–266)
1 34 6.56 (7.79) 0–29 (0–36)
Child dependency 2 30 3.60 (4.46) 0–17 (0–36)
1 38 5.89 (1.72) 1–7 (1–7)
DBC antisocial/disrup. 1 28 7.18 (6.86) 0–27 (0–54)
DBC self-absorbed 1 28 3.89 (4.46) 0–21 (0–62)
DBC communication 1 28 1.79 (2.44) 0–10 (0–26)
DBC anxiety 1 28 2.89 (2.87) 0–11 (0–18)
DBC social 1 28 1.54 (2.22) 0–9 (0–20)
DBC total score 1 28 18.82 (16.34) 0–60 (0–192)
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Independent Samples Tests for Distress and Child Behaviour Problems

Reported levels of distress, as measured by the GHQ-12, did not significantly differ across the two groups t(68) = −0.84, pb = 0.40. Problematic behaviour, as measured by scores on the ECBI problem subscale, also did not significantly differ between the samples, t(64) = −1.732, pb = 0.08. However, the intensity of child behaviour problems, as measured by scores on the ECBI intensity subscale, approached statistical significance t(64) = −1.911, pb = 0.05.

Correlations Between Parent-Report Measures and Distress

Phenylketonuria Group

Scores on the GHQ-12 were positively correlated with all measures of child behaviour, with a significant relationship emerging between anxious subscale of the DBC and the GHQ-12 score (r = 0.45; p < 0.05) (see Table 2). A highly significant negative correlation was found between scores on the GHQ-12 and the RSA, p < 0.01. Negative correlations emerged between the GHQ-12 score and subscales of the MSPSS, except for the friend subscale, which was very minimally positively correlated with GHQ-12 score. The child dependency scale scores were positively correlated with the GHQ-12, and significantly positively correlated with subscales of the DBC p < 0.05; p < 0.01.

Table 2.

Correlations between parent-report measures for participants for PKU group

1 2 3 4 5 6 7 8 9 10 11 12 13 14
1. MSPSS sig. other
2. MSPSS family 0.61**
3. MSPSS friend 0.49* 0.30
4. MSPSS total score 0.86** 0.77** 0.77**
5. ECBI problem −0.14 −0.35 0.24 −0.08
6. ECBI intensity −0.32 −0.49* −0.08 −0.36 0.72**
7. GHQ-12 total score −0.08 −0.31 0.07 −0.12 0.11 0.18
8. RSA total score 0.00 0.17 0.03 0.08 −0.04 −0.18 −0.52**
9. DBC disruptive −0.19 −0.29 0.08 −0.15 0.65** 0.67** 0.23 −0.10
10. DBC self-absorbed −0.60** −0.73** −0.35 −0.68** 0.55** 0.73** 0.11 −0.10 0.59**
11. DBC communicate −0.38* −0.66** −0.17 −0.48* 0.37 0.56** 0.27 −0.22 0.61** 0.67**
12. DBC anxiety −0.28 −0.36 −0.11 −0.30 0.26 0.38 0.45* −0.19 0.54** 0.38 0.53**
13. DBC social relating −0.15 −0.33 0.20 −0.10 0.48* 0.38 0.11 0.00 0.71** 0.45* 0.62** 0.56**
14. DBC total score −0.40* −0.55** −0.09 −0.41* 0.59** 0.71** 0.28 −0.15 0.90** 0.77** 0.82** 0.72** 0.79**
15. Child dependency −0.10 −0.28 0.11 −0.10 0.40* 0.50** 0.17 −0.13 0.33 0.30 0.28 0.48** 0.43* 0.42*
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*p < 0.05, **p < 0.01

Additional correlation analyses revealed significant negative associations between child age and the self-absorbed subscale of the DBC (Pearson’s r = −0.45, p < 0.05) and the intensity subscale of the ECBI (Pearson’s r = −0.49, p < 0.05). All other non-significant relationships were negative, except for the social-relating subscale of the DBC, which was positive (Pearson’s r = 0.12, p = 0.55).

Reference Group

The GHQ-12 was negatively correlated with all subscales of the MSPSS, although these were non-significant (see Table 3). A small positive correlation emerged between the intensity subscale of the ECBI and scores on the GHQ-12, p > 0.05. By contrast, a negative correlation was found for scores on the GHQ-12 and the problem subscale of the ECBI, p > 0.05. Subscales of the MSPSS were highly significantly positively correlated with each other, indicating a degree of overlap between these constructs, p < 0.01. Scores on the RSA were positively correlated with subscales of the MSPSS, with a significant correlation found for the friend subscale. RSA scores were positively correlated with the problem subscale of the ECBI and negatively correlated with the intensity subscale, although these were non-significant, p > 0.05.

Table 3.

Correlations between parent-report measures for Reference group

1 2 3 4 5 6 7
1. MSPSS sig. other
2. MSPSS family 0.91**
3. MSPSS friend 0.87** 0.84**
4. MSPSS total 0.97** 0.96** 0.95**
5. ECBI problem −0.08 −0.02 −0.09 −0.07
6. ECBI intensity −0.24 −0.22 −0.21 −0.24 0.22
7. GHQ-12 −0.03 −0.10 −0.06 −0.06 −0.24 0.02
8. RSA total score 0.28 0.21 0.37* 0.30 0.09 −0.08 −0.20
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*p < 0.05, **p < 0.01

Further correlation analysis revealed a positive correlation between child age and the problem subscale of the ECBI (Pearson’s r = 0.09, p = 0.66), indicating that behaviour difficulties in older children were considered to be more problematic for parents in this group. By contrast, a negative relationship emerged between child age and the intensity subscale of the ECBI, suggesting that younger children experience a higher incidence of behaviour problems (Pearson’s r = −0.24, p = 0.21).

Predictors of Psychological Distress

The anxiety subscale of the DBC and RSA total scores were entered into the regression model based on their significant correlations with the GHQ-12 (p < 0.01 and p < 0.05, respectively; Table 4) and similar findings reported in the literature (Medford et al. 2017a). Together, these variables explained 35% of the variance in GHQ-12 scores. RSA total scores was a significant predictor variable (Finalβ = −0.45, p < 0.05), but the anxiety subscale of the DBC was not (Finalβ = 0.36, p = 18).

Table 4.

Multiple regression analysis to examine the predictors of parental distress

Enter B SE B Finalβ p R2 F change
Criterion variable: GHQ-12 total [PKU group]
RSA total score −0.06 0.02 −0.45 0.04*
DBC anxiety 0.36 0.23 0.36 0.18 0.35 8.32**
Criterion variable: GHQ-12 total [Reference group]
RSA total score −0.09 0.03 −0.50 0.01
ECBI problem −0.02 0.04 −0.13 0.55
ECBI intensity −0.20 0.15 −0.25 0.15 0.19 3.25*
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F change *p < 0.05, **p < 0.01

No significant correlations were found between GHQ-12 scores and scores on measures of resilience, social support and child behaviour (problem and intensity subscales of the ECBI) for parents of children without PKU. Therefore, the intensity and problem subscales of the ECBI and RSA total scores were entered into the regression model to provide a model of distress in parents of children with PKU. These variables explained 19% of the variance in parents’ GHQ-12 scores. However, whilst RSA total scores was a significant predictor variable (Finalβ = −0.50, p < 0.01), the intensity and problem subscales of the ECBI were not (Finalβs = −0.13 and −0.25; p = 0.55 and 0.15, respectively).

Discussion

Contrary to the first research hypothesis, levels of distress were generally low for parents of children with PKU and were non-significantly different to parents in the general population. This indicates good parental well-being in this clinical population, which is consistent with studies demonstrating comparable levels of distress to reference groups and parents of children with other biochemical conditions (Kazak et al. 1988; Ten Hoedt et al. 2011a, b). However, it is possible that parental distress could have been masked by the low specificity of the GHQ-12 in the current study.

In accordance with the second hypothesis, parents of children with PKU reported a higher intensity of child behaviour problems, as measured by the ECBI intensity subscale, compared to those in the general population, which approached statistical significance. Parents of children with PKU also reported more problematic behaviours, as measured by the problem subscale of the ECBI, than those in the general population, although this difference was non-significant. These findings are consistent with the relevant research (Smith and Knowles 2000). Interestingly, for parents of children with PKU, psychological distress was positively correlated with greater satisfaction with social support from friends. One possible explanation for this is that parents of children with PKU who seek support from other parents may draw negative comparisons between their children and feel more distressed as a result.

Although scores on measures of child behaviour were generally low, mean scores on the DBC were highest for antisocial/disruptive behaviour, indicating a relatively higher prevalence of this form of behaviour. Problems with social relating were positively correlated with child age, which is in line with research indicating lower social competence in adolescents with PKU (Brumm et al. 2010). Negative trends were observed between child age and all other subscales of the behaviour measures, suggesting that younger children may experience a higher rate of behaviour problems generally, particularly self-absorbed behaviour, and behaviour related to anxiety was significantly correlated with parents’ distress. These trends are consistent with the relevant research (Craig et al. 2016; Jahja et al. 2013; Ten Hoedt et al. 2011a, b).

To address the third hypothesis, a multiple regression analysis was carried out to determine the predictors of parents’ distress. Consistent with the hypothesis, anxious behaviour in children and parents’ psychological resilience predicted distress in parents of children with PKU. Similar findings are reported in previous studies, with research demonstrating that psychological resilience is a predictor of parents’ distress than social support and child care dependency (Medford et al. 2017a) a finding echoed in the general population, suggesting that this not unique to parents of children with PKU. However, no significant correlations emerged between child anxious behaviour and distress for parents in this group. This suggests that the association between anxious child behaviour and parents’ distress could be unique to families affected by PKU; however, further research is needed to draw firm conclusions about this.

Critical Evaluation

The sampling method in the current study could have skewed the data by representing parents from higher socioeconomic backgrounds, who are currently accessing support and who experience lower levels of distress. The cross-sectional design of the study also makes it difficult to infer a causal relationship between child behaviour problems and parents’ distress. A further limitation of the current study was the lack of data on biomedical factors such as blood Phe concentrations or PKU genotype that might have an influence on child behaviour. Unfortunately, it was not possible to access this data for the present study and this omission should be rectified in further studies.

The sample size in the present study could have limited the validity of the findings. However, given the low prevalence of PKU, sample sizes in the literature have tended to be small (Ambler and Hare 2018).

Implications for Clinical Practice

Based on the findings in the current study, it is likely to be beneficial if support is tailored to enhance parents’ psychological resilience and the management of child behaviour problems, particularly anxious behaviour. Approaches such as Acceptance and Commitment Therapy (ACT) are shown to reduce distress in parents of children with autism (Blackledge and Hayes 2006) and could help build psychological resilience in parents of children with PKU through managing negative, yet accurate thoughts about the condition.

When assessing for anxious behaviour in clinical settings, routine screening using the DBC could help identify an unmet need for families affected by PKU.

Recommendations for Future Research

A longitudinal design would enable greater accuracy for observing external influences on parents’ distress, such as developmental trends. This could help further tailor support for families. To understand the potential causes of anxious behaviour in children and young people with PKU, it would be beneficial to measure this in relation to Phe levels, parenting practices and siblings’ behaviour. Future research with families from more diverse backgrounds could also help identify additional vulnerability factors for families.

Conclusion

Findings from this study suggest that levels of psychological distress are comparable between parents of children with PKU and those in the general population. However, children with PKU were reported to experience a higher incidence of behaviour problems than those in the general population. When building a model of distress for parents of children with PKU, multiple regression analysis showed anxious behaviour in children and psychological resilience in parents explained for 35% of the variance in distress. By comparison, generic child behaviour problems and psychological resilience accounted for only 19% of the variance in distress for parents in the general population. These findings build on existing research and further highlight the need to support families affected by PKU.

Synopsis

This research study identified that child anxious behaviour and parents’ psychological resilience explained 35% of the variance in parents’ distress in families affected by PKU, whereas child behaviour problems and parents’ resilience explained 19% of the variance for parents in the general population.

Details of the Contributions of Individual Authors

Dr. Olivia Ambler contributed to planning the research design, carrying out all aspects of the method and statistical analysis and writing the majority of the manuscript.

Dr. Emma Medford contributed to planning the research design and planning the method.

Dr. Dougal Julian Hare contributed to planning the research design, method, interpretation of the findings and preparation of manuscript.

Corresponding Author

Dr. Dougal Julian Hare.

Conflict of Interest

The authors declare that there was no conflict of interest.

Details of Funding and Ethics Approval

This study was funded by Cardiff University as part of the South Wales Doctorate Programme in Clinical Psychology.

Ethical approval was obtained from Cardiff University School of Psychology Ethics committee (EC.16.07.12.4554A2).

Informed Consent

Informed consent was obtained from the participants as part of the remit of ethical approval from Cardiff University School of Psychology Ethics Committee (EC.16.07.12.4554A2).

Contributor Information

Dougal J. Hare, Email: HareD@cardiff.ac.uk

Collaborators: Matthias Baumgartner, Marc Patterson, Shamima Rahman, Verena Peters, Eva Morava, and Johannes Zschocke

References

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