Bipolar disorder and comorbid attention deficit hyperactivity disorder. A distinct clinical phenotype? Clinical characteristics and temperamental traits

Objectives. It has been suggested that bipolar disorder (BD) with comorbid ADHD represents a distinct clinical phenotype of BD. There are no data regarding potential heterogeneity between BD subjects with a diagnosis of ADHD in childhood whose ADHD remitted in adulthood (cADHD-BD) vs. BD patients with persistent ADHD diagnosis in adulthood (aADHD-BD). This heterogeneity may constitute a confounder in investigations of the nature of the co-occurrence between BD and ADHD. The aim of this paper is to compare BD patients without ADHD, to those with aADHD-BD, and those with cADHD-BD on clinical and temperamental characteristics, hypothesizing that maladaptive temperament will be increased in BD subjects with a stable diagnosis of ADHD in adulthood compared to those whose ADHD remitted. We further hypothesize that maladaptive temperament will be associated with the severity of both illnesses. Methods. A total of 100 outpatients (aged 18-30 years) with BD in remission were included. The assessment of ADHD was made according to a procedure aimed to reduce potential recall biases. Subjects had to have a parent available and had never been treated with stimulants. Temperamental traits were assessed with the California Child Q-sort (CCQ) and the Early Adolescent Temperament Questionnaire (EATQ). Results. Rate of co-occurrence of ADHD-BD was 18% lifetime and 10% current diagnosis. Patients with ADHD-BD (aADHD-BD+cADHD-BD) reported a significantly earlier onset of mood disorder, higher number of previous mood episodes, and significantly higher impulsivity than BD patients without ADHD. aADHD-BD showed a significantly earlier BD onset, higher number of previous mood episodes, higher impulsivity, decreased Reactive Control and higher Negative Emotionality temperamental scores than cADHD patients. Conclusion. Findings suggest that patients with aADHD-BD present a clinical phenotype distinct from that of patients with BD without ADHD or with a childhood ADHD diagnosis that remitted with the age. This appealing hypothesis of a BD-distinct phenotype that can be detected early due to its associated maladaptive temperamental traits requires further investigation in larger samples, supported by neuropsychological, genetic and imaging data.