Since approximately 70% of adult patients with attention-deficit/hyperactivity disorder (ADHD) have at least one comorbid disorder, rating of impairment specifically attributable to ADHD is a hard task. Despite the evidence linking environmental adversities with negative outcomes in ADHD, life events measures have not been used to rate the disorder impairment. The present study tested for the first time the hypothesis that increased ADHD severity is associated with an increase in negative recent life events, independently of comorbidity status. The psychiatric diagnoses of 211 adult ADHD outpatients were based on DSM-IV criteria assessed through structured interviews (K-SADS-E for ADHD and ODD, MINI for ASPD and SCID-IV-R for other comorbidities). ADHD severity was evaluated with the Swanson, Nolan and Pelham rating scale (SNAP-IV) and recent life events with the Life Experience Survey. Higher SNAP-IV inattention and hyperactivity scores, female gender, lower socioeconomic status and the presence of comorbid mood disorders were associated with negative life events. Poisson regression models with adjustment for possible confounders confirmed the effect of inattention and hyperactivity severity on negative life events. Our results suggest that the negative life events experienced by these patients are associated to the severity of ADHD independently from comorbid psychiatric disorders.

Neuropsychological deficits in adults with ADHD go beyond comorbidity. Specific comorbid disorders may influence the neuropsychological functioning in adults with ADHD.

Polymorphisms in the CHRNA5-CHRNA3-CHRNB4 gene cluster have been shown to be involved in tobacco smoking susceptibility. Considering that attention deficit/hyperactivity disorder (ADHD) not only increases the risk but may also influence the molecular mechanisms of tobacco smoking, we analyzed the association between polymorphisms in the nicotinic acetylcholine receptor genes and tobacco smoking among individuals with or without ADHD. The sample included 1,118 subjects divided into four groups according to smoking status and ADHD diagnosis. Our results demonstrate that the minor alleles of two polymorphisms (rs578776 and rs3743078) in the CHRNA3 gene are associated with an increased risk of tobacco smoking only among patients with ADHD. These alleles have been shown in previous studies to be protective factors for smoking in subjects without ADHD. These findings add to existing evidence that ADHD may exert an important modifying effect on the genetic risk of smoking and should be considered in tobacco smoking association studies.

WCST impairments among patients with ADHD seem to be to a large extent attributable to comorbid BD. Although other executive function deficits (e.g., in the inhibitory control domain) have been demonstrated to accompany ADHD, the present findings suggest that set-shifting deficits are strongly related to comorbid BD.

Several lines of evidence suggest a relevant role for the dopamine transporter (DAT1) gene not only as a susceptibility factor for attention-deficit hyperactivity disorder (ADHD), but also as a predictor of individual methylphenidate (MPH) response. Pharmacogenetic studies of MPH response in ADHD have mainly focused on the 40-bp variable number of tandem repeats (VNTR) in the 3' untranslated region (3'-UTR) of DAT1. Most studies were performed in samples of children and conflicting findings were obtained. Only two studies have assessed 3'-VNTR in samples of adults-one with positive and the other with negative findings. In the present study, we investigate three potentially relevant polymorphisms in DAT1 gene (-839 C > T; Int8 VNTR and 3'-VNTR), and their possible role in therapeutic response to MPH treatment in a sample of 171 Brazilian adults with ADHD. The diagnostic procedures followed the DSM-IV criteria and the outcome measures were the scales Swanson, Nolan, and Pelham Rating scale version IV and the Clinical Global Impression-Severity Scale, applied at the beginning and after the 30th day of treatment. Drug response was assessed by both categorical and dimensional approaches. There was no effect of any DAT1 polymorphisms or haplotypes on MPH response. This is the second report demonstrating absence of differences in MPH response according to DAT1 genotypes in adults with ADHD. Although DAT protein is crucial for the effect of MPH, genetic variations in DAT1 gene probably do not have a significant clinical role in this sample of adults with ADHD.