Is ADHD a risk for posttraumatic stress disorder (PTSD)? Results from a large longitudinal study of referred children with and without ADHD

Objectives. Preclinical studies link prenatal nicotine exposure with the development of both ADHD-like phenotype in rodents and blockade of extinction learning in a fear conditioning paradigm, a preclinical model of posttraumatic stress disorder (PTSD). While these findings suggest that either ADHD, prenatal nicotine exposure, or both could be a risk factor for PTSD, such associations have not been investigated in humans. Methods. Subjects were ascertained from family-genetic, longitudinal studies of paediatrically and psychiatrically referred children with and without ADHD of both sexes and their siblings followed for 10 years from childhood into adulthood (n = 403 probands; n = 464 siblings; mean age at follow-up of probands and siblings = 22.0 years). All subjects were comprehensively evaluated with structured diagnostic interviews that included questions regarding prenatal use of cigarettes. Results. A total of 12% (104/867) of the sample had been exposed to maternal smoking during pregnancy. There was no interaction effect between maternal smoking during pregnancy and ADHD (z = 0.01, P = 0.99). Maternal smoking during pregnancy and ADHD were independent, significant risk factors for PTSD at the 10-year follow-up (odds ratio = 3.58 [1.35,9.48], z = 2.57, P = 0.01 and odds ratio = 2.23 [1.06,4.69], z = 2.11, P = 0.04, respectively). Conclusions. These results suggest that both maternal smoking during pregnancy and ADHD are significant predictors of PTSD in humans.