Elsevier

Biological Psychiatry

Volume 71, Issue 5, 1 March 2012, Pages 474-481
Biological Psychiatry

Archival Report
Pre- and Perinatal Risk Factors in Adults with Attention-Deficit/Hyperactivity Disorder

https://doi.org/10.1016/j.biopsych.2011.11.013Get rights and content

Background

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent and disabling lifespan disorder, but little is yet known about risk factors for ADHD persisting beyond adolescence. The present study investigates the association between pregnancy and birth complications and ADHD in adulthood.

Methods

We used data from the Medical Birth Registry of Norway to compare pre-and perinatal risk factors among 2323 adults approved for medical treatment for ADHD, with the remaining population born during the same years, 1967–1987, and surviving into adulthood (n = 1,170,073). Relative risks (RR) adjusted for potential confounders were calculated.

Results

Preterm (< 37 weeks of gestation) and extremely preterm birth (< 28 weeks of gestation) were associated with 1.3- and 5-fold increased risks of ADHD, respectively. Birth weights <2500 g and <1500 g also increased the risk of ADHD (RR: 1.5, 95% confidence interval [CI]: 1.2–1.8, and RR: 2.1, 95% CI: 1.3–3.6, respectively). Five-minute Apgar scores <4 and <7 were associated with 2.8- and 1.5-fold increased risks of persisting ADHD, respectively. Maternal epilepsy (RR: 1.7, 95% CI: 1.1–2.7) and offspring oral cleft (RR: 2.8, 95% CI: 1.6–4.9) occurred more frequently among adult ADHD patients.

Conclusions

This is the first population-based study of pre-and perinatal risk factors in adults with ADHD. We show that low birth weight, preterm birth, and low Apgar scores increase the risk of ADHD, persisting up to 40 years after birth. The increased risk of ADHD related to oral cleft and to maternal epilepsy warrants further investigation to explore possible causal mechanisms.

Section snippets

Materials and Methods

We performed, on the basis of data from the Medical Birth Registry of Norway (MBRN), a population-based nested case-control study, where cases were 2323 adult ADHD patients and control subjects were the remaining general population registered in the MBRN, born in the same time period (1967–1987) and surviving into adulthood (n = approximately 1.17 million).

Sociodemographic Data

Table 1 shows that the proportion of men was higher among ADHD patients than in the general population and that patients on average were younger (i.e., a higher proportion was born in the later years of the study period). The mean age of the ADHD patients at the time of inclusion into the study was 31.2 years, compared with 32.6 years for the rest of the birth cohort (SDs 5.8 and 6.1, respectively, p < .001, t test, independent samples). Furthermore, patients more often had the lowest level of

Discussion

This population-based investigation is the largest study on pre- and perinatal risk factors for ADHD and the first performed on adults clinically diagnosed with ADHD. Intrauterine growth restriction, preterm birth, LBW, and low Apgar scores were associated with an increased risk of ADHD in a national birth cohort of adults. The study thus confirms earlier findings on children with ADHD, and further expands the evidence that intrauterine factors play a role in the risk of developing ADHD that

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