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Parental Age and the Risk of Attention-Deficit/Hyperactivity Disorder: A Nationwide, Population-Based Cohort Study

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Objective

An increasing number of studies has shown an association between parental age and psychiatric disorders. However, there are inconsistent results regarding whether age at parenthood is associated with attention-deficit/hyperactivity disorder (ADHD). The aim of this study is to examine whether low or advanced parental age is associated with ADHD.

Method

In this nested case-control study, we identified 10,409 individuals with ADHD born in Finland during 1991 to 2005 and diagnosed with ADHD between 1995 and 2011, along with 39,125 controls matched on sex, date, and place of birth, from nationwide population-based registers. Conditional logistic regression was used to examine the association between parental age and ADHD in offspring, adjusting for potential confounding due to parental psychiatric history, maternal socioeconomic status, marital status, maternal smoking during pregnancy, number of previous births, and birth weight for gestational age.

Results

Fathers younger than 20 years had a 1.5-fold (odds ratio [OR] = 1.55, 95% CI = 1.11–2.18, p = .01) increased risk of having offspring with ADHD as compared to fathers aged 25 to 29 years. Mothers of the same age group had a 1.4-fold (OR = 1.41, 95% CI = 1.15–1.72, p =.0009) increased risk. Advanced maternal age was inversely associated with ADHD (OR = 0.79, 95% CI = 0.64–0.97, p = .02).

Conclusion

ADHD was associated with young fathers or mothers at the time of birth. Health professionals working with young parents should be aware of the increased risk of ADHD in offspring. This will improve early detection; however, for the development of preventive measures and appropriate interventions, more information on the developmental pathways is needed.

Section snippets

Study Design

This study is based on the Finnish Prenatal study of ADHD (FIPS-ADHD). It is a nested case-control study derived from all singleton live births in Finland between January 1, 1991 and December 31, 2005 (N = 900,603) (Figure 1). The total number of participants includes all those diagnosed with ADHD, identified from the Finnish Hospital Discharge Register (FHDR) between January 1, 1995, and December 31, 2011. The controls were selected randomly from the remainder of the national cohort who were

Results

Table 2 shows the paternal and maternal age distribution for participants with ADHD and controls. The paternal age among those with ADHD ranged from 16 to 67 years (mean = 30.6 years, SD = 6.5 years). Maternal age ranged from 14 to 47 years (mean = 27.8 years, SD = 5.7 years). As shown in Table 1, all of the potential confounders were significantly associated with both paternal and maternal age among controls as well as with ADHD. Parental ADHD was associated with having children at an earlier

Discussion

Young parental age was associated with an increased risk of ADHD. Fathers and mothers younger than 20 years had the highest risk of having an offspring with ADHD. However, offspring of mothers older than 30 years had a decreased risk of ADHD. The finding of an increased risk of ADHD in offspring of young parents is in line with previous studies. An increased risk of ADHD has been seen in offspring with young mothers9, 15, 16 and fathers.9 Offspring with both parents younger than 20 years had a

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      Previous studies have provided good evidence that young, as well as advanced, parental age have been associated with several psychiatric disorders in offspring. Young parental age has been linked with offspring attention deficit hyperactivity disorder (Chudal et al., 2015), psychosis (Miller et al., 2011), bipolar disorder (Chudal et al., 2014) and substance use (McGrath et al., 2014). On the other hand, advanced parental age has been associated with psychosis (Miller et al., 2011; D'Onforio et al., 2014), autism (Hultman et al., 2011; Sandin et al., 2012; D'Onforio et al., 2014), bipolar disorder (Menezes et al., 2010; Chudal et al., 2014, D'Onforio et al., 2014) and suicide attempts (D'Onforio et al., 2014).

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    Clinical guidance is available at the end of this article.

    The study was supported by grants from the National Alliance for Research on Schizophrenia and Depression Independent Investigator Award, USA (A.S.), the Sigrid Juselius Foundation, Finland (A.S.), and Academy of Finland (A.S.). The study was conducted at University of Turku, Finland.

    Ms. Hinkka-Yli-Salomäki served as the statistical expert for this research.

    Disclosure: Drs. Chudal, Joelsson, Gyllenberg, Lehti, Leivonen, Gissler, Sourander, and Ms. Hinkka-Yli-Salomäki report no biomedical financial interests or potential conflicts of interest.

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