The Effects of Parenting Styles on Internalizing and Externalizing Behaviors: A Mexican Preadolescents Study

Abstract.

Parental practices such as inconsistent discipline, psychological control, and imposition have been linked to the development of internalizing and externalizing problem behaviors in preadolescents. This study aimed to identify the association these practices had on Mexican preadolescent problem behaviors through Structural Equation Modeling. The sample consisted of 306 elementary students from three public schools in Mexico City (age M = 10, SD = 0.92). Students completed subscales from the Parental Practice Scale, the Alabama Parenting Questionnaire, and the Strengths and Difficulties Questionnaire. Paternal imposition and maternal psychological control were significant predictors for internalizing problems, while inconsistent discipline was a significant predictor of externalizing problems. The results highlight that although parental practice values might differ across cultures, their association to problem behaviors are similar.

1.Introduction

Preadolescence is a critical moment in development, as many factors dictate the path from childhood into adolescence and, most importantly, from adolescence to adulthood. It is understood as a point of inflexion due to conflicting developmental demands for greater autonomy (Kader & Roman, 2018; Laursen & Collins, 2009). It is an influential moment given that the quality of emotional bonds and experienced parenting practices will either be constituted predecessors of protective factors and regulatory skills as adolescents (Galaz, Manrique, Ayala, Mota, & Díaz-Loving, 2019) or influence the development of externalizing and internalizing problem behaviors (Cox, 2014; Cutrín, Maneiro, Sobral, & Gómez-Fraguela, 2019).

There is general consensus in self-determination theory that autonomy-discouraging parenting exerted through controlling, pressuring, and manipulative practices undermines youth adjustment and well-being (Soenens, Vansteenkiste, & Sierens, 2009). It is parental pressure, intrusiveness, and domination that assault children’s individuality and therefore hinders children’s psychological development and autonomy (Grolnick & Pomerantz, 2009).

According to UNICEF México (2017), there are 39.2 million children and adolescents in Mexico, more than half of them are living in poverty and suffering psychological abuse in their households, thus Mexico was placed within the worst three countries in Latin America in relation to child rearing (UNICEF México, 2017). Although less than 7% have openly reported experiencing physical punishment from their parents, the majority of the adolescents have expressed enduring overly-harsh parental practices. During 2014, the National system for the Integral Development of Families in Mexico (DIF) reported nearly 40,000 investigations related to child maltreatment; the second and third most common causes being physical and emotional parental maltreatment of children and adolescents (Sotelo & FUPAVI., 2015).

The Mexican society is a hierarchical structure based on respect (respeto) towards others higher in the social structure (specifically parents and relatives). Respeto is understood as an orientation of maintaining amicable interpersonal relationships based on the demonstration of respect for self and others and an appreciation of each family member’s unique role. Familismo, on the other hand, is conceptualized as upholding the belief of duty towards the family by staying together, keeping strong family ties, and placing commitment to the family over individual desires and needs (Lindsey, 2018). Overall, duty and respect towards the family are viewed as the foundation for adequate family functioning and are therefore instilled by Latinx parents (Lindsey, 2018). In a collectivistic society such as Mexico where family loyalty and hierarchy are placed above an individual’s desires (Calzada, Barajas-Gonzalez, Huang, & Brotman, 2015), autonomous regulation, as proposed by self-determination theory (B. K. Barber, Stolz, Olsen, Collins, & Burchinal, 2005; Marbell-Pierre, Grolnick, Stewart, & Raftery-Helmer, 2019), might be much more difficult to achieve, thus placing Mexican preadolescents in a more vulnerable position to social maladjustment and psychopathology.

Mexican children and adolescents perceive their father as someone who is caring and hardworking. Because fathers are providers they are seen as the principal authority figure in the family and therefore demand respect. According to Parra, Estrada, van Barneveld, Montiel, and López (2014), fathers provide behavioral cues, limits, discipline and assistance to primary needs. Meanwhile, mothers are seen as loving, helpful, protective, and responsible. It is a figure that scolds when necessary while being more understanding than fathers, and overall someone that is much more involved and supportive to the child’s activities (Galaz et al., 2019; Varela, Castañeda, Galindo, Moreno, & Salguero, 2019). This explains why maternal practices are overall perceived more positively and have a higher impact in children as opposed to paternal practices (Cox, 2014; García Linares, Cerezo Rusillo, de la Torre Cruz, Carpio Fernández, & Casanova Arias, 2011; Kline, Killoren, & Alfaro, 2016).

In parenting terms, preadolescence is seen as a moment in which direct parental control and supervision decline and parents begin exerting a more distant form of parenting, in order to allow successful preadolescent development (Eguiarte & Arenas, 2019). Latinx parents exert control over preadolescents (in the forms of disciplinary or psychological practices) with the purpose of successfully integrating their new identities into the family and into society. It is through practices of control that parents shape and evaluate their children’s obedience, which consequently derives in preadolescent autonomy (Varela et al., 2019).

Externally controlling parental practices such as imposition and discipline make preadolescents feel pressured to meet parental requirements. Regulation is imposed by thoughts and feelings of being punished, rewarded or pressured; nonetheless, externally controlling practices are more likely to result in a lack of compliance to parental authority. Internally controlling parental practices such as psychological control act by an internal compulsion in the preadolescent to engage in the requested behavior. In this case, regulation results from introjecting the parental demands that activate internal pressures in children, such as guilt, shaming or self-criticism, while also resulting in a mixture of ambiguous feelings towards parents (Assor, Vansteenkiste, & Kaplan, 2009; Soenens & Vansteenkiste, 2010).

Inconsistent discipline is characterized by its unpredictability and incongruence. This pattern becomes problematic as it favors children’s impossibility to re spect and maintain limits or adequately develop behavior self-regulation (Halgunseth, Perkins, Lippold, & Nix, 2013). The resulting parenting environment becomes chaotic and unpredictable for children and preadolescents, affecting not only the parent-child relationship, but the child’s perceptions of both parents and his or her own self (Beck & Haigh, 2014). Parents that use inconsistent disciplinary practices set limits unevenly, enforce consequences discrepantly, and can, in turn, become highly rigorous and punitive (Belsky, Schlomer, & Ellis, 2012), which results in a higher prevalence of externalizing problems, a worse parent-child relationship, and decreased autonomy in children (Grolnick & Pomerantz, 2009; Omer, Satran, & Driter, 2016).

When parents communicate roles and limits through disciplinary practices, they provide children with a clear set of guidelines for appropriate behavior, making them feel more comfortable with their parents, have a closer parent-child relationship, self-regulate earlier than their counterparts, and accept discipline with greater ease (Aguilar-Yamuza, Raya-Trenas, Pino-Osuna, & Herruzo-Cabrera, 2019; Soenens & Vansteenkiste, 2010). In contrast, inconsistent disciplinary practices fail to provide sufficient and clear cues for socially acceptable behavior in children, which results in the development of externalizing problems (Hill, Witherspoon, & Bartz, 2018; Holtrop, McNeil Smith, & Scott, 2015; Marchand-Reilly, 2012; Pouliot-Lapointe, Gagné, Drapeau, & Saint-Jacques, 2014; Raya Trenas, Pino-Osuna, & Herruzo-Cabrera., 2012).

Paternal Imposition is defined as parental behaviors used to punitively and forcefully dictate beliefs and behaviors to limit or eliminate undesirable conducts regardless of the desires and needs of children (Musitu & García, 2004). It consequently derives in children a sense of anger towards their parents and later develops both internalizing and externalizing problem behaviors, while promoting fear and inhibition towards authority figures, thus hindering the development of an adequate parent-child relationship (González & Garcia, 2014).

González-Forteza, Echeagaray, and Jiménez Tapia (2012) measured the impact parental imposition had on Mexican preadolescents and corroborated previous findings in which paternal imposition was a precursor to both problem behaviors. Unlike other studies, (Méndez, Andrade Palos, & Peñaloza, 2013) demonstrated that parental practices of imposition solely predicted externalizing problems in Mexican preadolescents.

By using adequate disciplinary practices and imposition, Mexican parents can influence their youth to treat family members with respeto, reinforcing authority hierarchies and clarifying the social norms they are expected to follow.

Psychological control is defined as parental behaviors of cognitive, emotional, and love manipulation through excessive criticism, affect withdrawal, and emotion invalidation. Alike imposition, practices of psychological control involve guilt induction and evocation of concern to control a child’s behavior through emotional mechanisms (Andrade Palos et al., 2012; B. Barber, 1996; Gutiérrez, Madrigal-De León, & Martínez-Munguía, 2018). The resulting paternal environment becomes highly stressful and demanding for a child, resulting in a higher prevalence of both internalizing and externalizing problem behaviors and parental dependency in children that experienced more psychological control than their counterparts (Borda Mas et al., 2019; Kiel & Buss, 2011).

In Mexico, parental psychological control has been specifically associated to externalizing problem behaviors (Betancourt, 2007) and to both problem behaviors (Andrade Palos & Betancourt Ocampo, 2012; González-Forteza et al., 2012; Méndez et al., 2013). Surprisingly, paternal psychological control was related to lower levels of internalizing behaviors as teenagers feel closeness and interest from their fathers, which acts as a protective factor (Cruz, Narciso, Pereira, & Sampaio, 2014; González Lugo, Pineda Domínguez, & Gaxiola Romero, 2018).

In contrast to behavioral cues given by discipline and imposition, psychological control might serve a dual purpose in both directing children towards a role parents expect them to fulfill, while also modeling a system of beliefs in which Familismo is emphasized.

In order to provide Latinx parents with information and methods to support preadolescent development, the present study aims to shed some light on the association these negative parental practices have on the development of internalizing and externalizing problem behaviors in a sample of Mexican preadolescents through Structural Equation Modeling. SEM was chosen over traditional methods to counteract measurement challenges (such as preadolescent scale validity) and as a way to examine simultaneous parental practices on both problem behaviors (Soenens & Vansteenkiste, 2010). In contrast to most parenting literature with Latino samples, this project focuses solely on youth-perceived parental practices and self-reported problem behaviors.

Our main hypotheses were:

1. A significant association between inconsistent discipline and externalizing problem behaviors.

2. Significant associations from imposition and psychological control to both problem behaviors.

Our secondary hypotheses were:

1. Greater effects from maternal practices when compared to paternal.

2. Significant differences by sex and grade in problem behaviors and parental practices.

2. Method

2.1 Sample

This ex post facto cross-sectional study had a nonprobabilistic sample; participants were collected from three public elementary schools in the southern part of Mexico City during 2018 spring. The project was carried out following the Mexican Psychological Society’s code of ethics (Sociedad Mexicana de Psicología, 2010). Prior to data recollection, participants, parents, and schoolstaff were informed about reaches, potential risks, and confidentiality. The application team emphasized the confidentiality of the process and asked the students to answer the questionnaire anonymously. All students from 4th, 5th, and 6th grades were eligible, but were selected only if they were in school during the application and if their parents had signed their informed consent.

Students were handed out a booklet containing all the scales and asking for their sex, age and grade. They were asked to read and then answer it with the help of a teacher who would read the items out loud to the class. The total sample was comprised by 306 students (48.8% girls, age M = 10, SE = 0.92) from 4th (33%), 5th (31%), and 6th (36%) grades. 69% of them lived with both their parents in a same household.

2.2 Instruments

Maternal and paternal practices of psychological control and imposition were measured using the subscales from Andrade and Betancourt’s (2008) Parental Practices Scale in its reduced version (Segura, Vallejo, Osorno, Rojas, & Reyes, 2011). The Parental Practices Scale is answered per parental figure with a Likert type scale (4 points, ranging from Never up to Always). The mother version has 15 statements derived from 5 factors (Communication, Psychological Control, Imposition, Behavioral Control, and Autonomy). The father version has 11 statements from 4 underlying dimensions (Communication, Psychological Control, Autonomy, and Imposition).

Inconsistent Discipline was measured with the subscale from Frick (1991) Alabama Parenting Questionnaire (APQ) in its Spanish version (Escribano, Aniorte, & Orgilés, 2013). The APQ consists of 16 statements that are answered using a 5 point Likert Type scale (ranging from Never to Always) derived from 4 underlying factors: Inconsistent Discipline, Positive Parenting, Poor Supervision, and Parental Involvement.

Internalizing and externalizing problems were measured using a Spanish translation (Rivera Gutiérrez, 2013) of the Strengths and Difficulties Questionnaire (SDQ) (Goodman, Ford, Simmons, Gatward, & Meltzer, 2000). The SDQ consists of 25 statements that are agreed upon using a Likert-type scale (3 points ranging from Never to Always), where higher scores indicate higher presence of problem behaviors.

2.3 Procedure

Firstly, questionnaires with more than 20% of missing answers were discarded (n=26). Initial data exploration, discrimination and missing data analyses were carried out to determine an imputation method and identify potential threats to reliability. Confirmatory Factor Analyses (CFAs) were run to verify subscale validities. If scales were found to be non-invariant, Exploratory Factor Analyses (EFAs) were carried out to extract valid and reliable measures in order to test our hypotheses.

2.4 Analysis

T-tests were performed to assess data MCAR for imputation purposes; two items from the SDQ were found to have data MNAR and were discarded. Missing data was managed by series mean imputation, never exceeding 16 cases per variable (<5% of the total). CFAs were deemed adequate if absolute fit was non-significant; both CFI and TLI were above .9 and the RMSEA was below .05. EFAs used principal component analysis with varimax rotation and followed Kaiser’s criterion. As to principal hypothesis testing, a Structural Equation Model was constructed using Mplus 7.1. The model was specified using negative parental practices as covarying exogenous variables. Internalizing and Externalizing problem behaviors were regressed on all parental practice factors except for inconsistent discipline for theoretical reasons. To avoid sample overfitting, three Lagrange Multipliers were allowed per factor. In all cases, the estimator used was Maximum Likelihood Mean and Variance (MLMV), given its robustness with non-normal data. The path diagram is presented as Figure 1. A series of mean comparisons were run in order to answer the secondary hypotheses, where a t-test was performed to find differences by sex and a One-Way ANOVA was run to find schoolyear differences in parental practices and problem behaviors.

Figura 1. Negative parental practices and their association to problem behaviors in Mexican preadolescents (covariances between practices not shown for clarity).

Note. mpc=maternal psychological control, ppc=paternal psychological control, mimp=maternal imposition, pimp=paternal imposition, icd=inconsistent discipline, int=internalizing problem behaviors and ext=externalizing problem behaviors.

3. Results

Both maternal and paternal Parental Practice Scales resulted in configurally invariant, fitting models with low errors of approximation and were used as reported: Maternal Psychological Control items 4-6 (α = .80), Maternal Imposition 7-9 (α = .81), Paternal Psychological Control items 3-5 (α = .83), and Paternal Imposition 9-11 (α = .72). On the other hand, CFAs for the APQ and SDQ depicted low and other non-significant factor loadings that evidenced configural or metric non-invariance (see Table 1), thus EFAs were carried out to extract valid and reliable measures for inconsistent discipline and problem behaviors. Both EFAs demonstrated sampling adequacy (KMOs>.75) and significant sphericity.

Table 1. Fit statistics for confirmatory factor analyses.

Scale	df	χ2	CFI	TLI	RMSEA	C.I	SRMR
PPSm	80	99.18	0.96	0.95	0.02	.00-.04	0.04
PPSf	38	40.22	0.98	0.98	0.01	.00-.04	0.04
APQ	98	134**	0.9	0.88	0.35	.01-.04	0.06
SDQ	57	181.56***	0.86	0.84	.04	.02-.05	0.05

Note. PPm: Parental Practice Scale (mother version), PPSf: Parental Practice Scale (father version), APQ: Alabama Parenting Questionnaire, SDQ: Strengths and Difficulties Questionnaire. **.01 ***.001

The Exploratory Factor Analysis on the APQ extracted three dimensions with 57% of explained variance. Inconsistent discipline was measured through items 10-13 (same items as the reported scale) and presented adequate internal reliability (α = .64). Regarding problem behaviors, the EFA extracted 3 factors with 61% of explained variance: Internalizing Problems were measured through items, 2, 5, 10, 15, and 18; Externalizing Problem Behaviors items 3, 8, 13, 16, and 24. Both subscales presented adequate internal reliabilities (α = .69 and α = .67, respectively). Resulting modifications of the questionnaires rendered adequate fit statistics for both instruments: APQ: S-B χ²(95) : 114.41(p > .05), CFI: .94, TLI: .93, RMSEA: .02. SDQ: S-B χ²(40) : 38.78(p > .05), CFI: 1, TLI: 1, RMSEA: .0.

As to the structural equation model, all factor loadings and latent variances were significant and the model presented good fit statistics S-B χ²(273):290.43(p > .05), CFI: .96, TLI: .95, RMSEA: .01. Lagrange multipliers suggested adding covariances between error terms of items APQ10 and 11 (items related to punishment), CFD2 and 10 (restlessness), CFD2 and 13 (hyperactivity and sadness), CFD15 and 16 (distraction and self-confidence), PPSf5 and 9 (blame and thought imposition), PPSf3 and PPSm4 (parents shouting and getting annoyed at preadolescents).

Structural coefficients indicate that paternal imposition is a fair predictor of internalizing problems (β =.6, p = .01). As to psychological control, maternal practices are predictors of internalizing problems (β = .45, p =.009) and surprisingly, paternal practices of psychological control had a negative effect on the development of externalizing problems (β = .2, p = .04). As expected, inconsistent discipline acted solely upon externalizing problems (β = .42, p = .003) and is considered a moderate predictor. Internalizing problems were significant and robust predictors of externalizing problems (β = .69, p < .000) (see Figure 1).

Both direct and indirect effects for both outcome variables account for a considerable amount of variance explained (Internalizing R2=39%) (Externalizing R2=68%). The only exogenous variable that did not report any direct or indirect effect to problem behaviors was maternal imposition.

As to mean comparisons, there were significant differences by sex in parental practices, where boys presented higher Paternal Imposition t(280.59) = 2.53(p = .01) and Externalizing behaviors t(293) = 2.02(p = .04). Schoolyear ANOVAs with Scheffé’s post-hoc test (as a measure to deal with unequal group sizes), resulted in differences for Internalizing F (2, 303) = 3.56(p = .02) and Externalizing problem behaviors F (2, 303) = 6.86(p = .004), where 4th graders reported significantly higher means for both when compared to 6th graders (Scheffé p = .03 and p = .001 respectively). Surprisingly, no significant differences in parental practices by grade were found

4. Discussion

The present model served the purpose of exploring the association simultaneous parental practices (Soenens & Vansteenkiste, 2010) have on preadolescent problem behaviors, as well as assessing both the constructs and measurements in a Mexican preadolescent sample. Fit statistics, factor loadings, and internal reliabilities demonstrate construct validity and reliability for the latent variables, despite having used parent oriented scales with preadolescents and using instruments that measure constructs derived from other samples in different cultures. It can be seen that all negative parental practices did present significant associations with both problem behaviors, thus indicating that for Mexican preadolescents, parental intrusion, domination, and manipulation hinder preadolescent psychological wellbeing (Cutrín et al., 2019; Grolnick & Pomerantz, 2009; Soenens et al., 2009).

In accord with previous findings (Hill et al., 2018; Holtrop et al., 2015; Marchand-Reilly, 2012; Pouliot-Lapointe et al., 2014; Raya Trenas et al., 2012), inconsistent discipline was a predictor of preadolescent externalizing problem behaviors in the Mexican culture as well, thus supporting our first hypothesis. This implies that by not consistently setting, supervising or enforcing limits, parents are neglecting to model their expectations (Beck & Haigh, 2014), thus worsening the parent-child relationship (Omer et al., 2016), weakening compliance to parental authority in the future (Assor et al., 2009) and developing distress in their children.

Table 2. Means, standard deviations and sumscale correlations.

	Mean	SD	1	2	3	4	5	6	7
Inconsistent Discipline	7.7	2.79	-
Paternal Imposition	3.78	1.56	.24**	-
Paternal Psychological	3.63	1.38	.21**	.31**	-
Control
Maternal Psychological	4.78	2.04	.28**	.17*	.33**	-
Control
Maternal Imposition	4.81	1.90	.28**	.42**	.20**	.38**	-
Internalizing Problem	8.33	2.42	.20**	.32**	.29**	.26**	.24**	-
Behaviors
Externalizing Problem	8.84	2.44	.28**	.23**	.13*	.23**	.21**	.51**	-
Behaviors

Note. _p < .05, _ _ p < .01

Specifically in Mexico, inconsistently disciplined preadolescents will probably not learn in time what is expected of them in a collectivistic society, how to treat others with respeto nor learn how to self-regulate themselves into healthier developmental outcomes, thus becoming more vulnerable to deviant peers and less autonomous than their counterparts.

In contrast to previous Mexican research (González-Forteza et al., 2012; Méndez et al., 2013) parental imposition was identified as a predictor of internalizing problem behaviors, which partially supports our second hypothesis. Despite being thought of as an externally controlling parental practice (Assor et al., 2009), this sample of preadolescents presented an emotional response rather than a behavioral one. This may be interpreted in the light of Familismo, where preadolescents would rather accept feeling guilty or shameful before being disloyal to their fathers by disobeying their demands (Galaz et al., 2019; Parra et al., 2014; Varela et al., 2019). Given that fathers are perceived as the highest authority figure in the Mexican family, it makes sense that paternal imposition had a stronger impact than maternal.

In previous Mexican studies (Andrade Palos et al., 2012; Andrade Palos & Betancourt Ocampo, 2012; Méndez et al., 2013), boys consistently present higher externalizing problem behaviors when compared to girls, and this study was not the exception. Externalizing problems can be understood as a discrepancy in Latinx family functioning, as parents cannot actively mitigate preadolescent misbehavior (Lindsey, 2018). Therefore, it is not surprising that boys also report higher levels of paternal imposition, despite there not being a significant effect between these two variables in the model.

Contrary to previous findings in Mexico and other countries (Betancourt, 2007; Kiel & Buss, 2011), psychological control was found to be a direct predictor of Mexican preadolescent internalizing problem behaviors only, partially supporting our secondary hypothesis as well (Andrade Palos et al., 2012; Borda Mas et al., 2019; González-Forteza et al., 2012; Méndez et al., 2013). This result is not surprising as Latinx mothers are more involved both emotionally and physically with their children (Galaz et al., 2019; Varela et al., 2019), thus resulting in successful psychological control through cognitive and emotional manipulation or love withdrawal, as children do not want their primary caregivers feel upset or go through hardships because of them (such as familsmo states), which activates the internal pressures in children to engage in behavior modification (Assor et al., 2009; Soenens & Vansteenkiste, 2010).

Surprisingly, paternal parental practices present more and even stronger associations to both preadolescent problem behaviors than maternal practices. This contrasts with previous Mexican and Latinx research, rebuffing our hypothesis about more salient maternal practices (Cox, 2014; García Linares et al., 2011). As to our last hypothesis, no differences in parental practices across grades were found. As to problem behaviors, the youngest third of our sample did present higher means for both problem behaviors, probably related to parental separation, yet a cross-sectional design does not provide strong support for this claim.

Paternal psychological control presented a negative relationship to preadolescent externalizing problem behaviors, replicating the findings of Cruz et al. (2014) and González Lugo et al. (2018) , which supports the claim that when Mexican preadolescents experience their father’s involvement in their emotional world, preadolescents felt closer and more appreciated by their fathers.

In conclusion, this study shows that although Mexico is a collectivistic country, where child rearing values and desirable outcomes differ from individualistic countries, the associations between parental imposition, psychological control, and inconsistent discipline with internalizing and externalizing problem behaviors are very similar between cultures.

As to the clinical applicability of the findings, family therapists working with Mexican samples should instate the benefits of consistent disciplinary practices complemented with communication to strengthen role clarity, responsibility in learning from past experiences, and parental accord in limit setting/enforcing through respect and mutual aid (Comino Velázquez & Raya Trenas, 2014). Providing information to parents about what to expect during preadolescence, in addition to strengthening communication between family members, will aid parents in disclosing their expectations and transmit them into adequate behavioral cues while being still recipient to preadolescent desires and needs. Sensitizing parents about the impacts negative parental practices have on preadolescents might be helpful in diminishing their use, thus aiding preadolescent development and autonomy.

There are a number of important limitations to this study, such as the use of some instruments originally derived for parents, self-report bias, a lax sampling procedure, and teacher data recollection. The use of self-report questionnaires might have resulted in biased answers from the sample, despite a confidentiality statement and relative privacy while answering. As for the instruments used, only the Parental Practice Scale was initially derived for children, which might explain the lack of psychometric robustness from the other two inventories regardless of the adaptation to preadolescents. Although valid and reliable subscales were extracted from the APQ and SDQ, the results should be interpreted with caution, as those measures were not designed to capture preadolescent perceptions on parental practices. Finally, working with preadolescents denotes some concerns on answer stability, given their own developmental process; therefore, longitudinal studies are strongly suggested when working with this sample. Despite our results, the cross-sectional design of this study cannot establish casual relationships between our variables.

The authors report that there are no conflicts of interest and that there was no funding involved in the development of this project. The main author would like to acknowledge the invaluable support of Dr. Tiffany A. Whittaker.