The Comorbilidad en Adultos con TDAH (CAT) study sought to characterise the psychiatric comorbidity profile associated with adult ADHD at the time of diagnosis with respect to prevalence, type and number of psychiatric illnesses in addition to their risk factors. The results indicated that psychiatric disorders are prevalent among adults with ADHD.
This observational, cross-sectional, multicentre study was conducted from April–November 2011. Participants were adults (n=367; aged >18 years) who had received a first-time diagnosis of ADHD* while attending appointments at psychiatric practices. Information on psychiatric comorbidities was obtained based on the participants’ clinical records, and other demographic and social information† was also collected. An evaluation of the history of tobacco, alcohol and substance abuse, self-injury and familial psychiatric conditions was conducted. The types of prescribed treatments were recorded and grouped into three categories: ADHD medication, medication for psychiatric comorbidities and non-pharmacological treatments.
Within the study sample, the combined ADHD (ADHD-C) subtype was the most prevalent (42.1%), followed by the hyperactive/impulsive (ADHD-H) [31%] and the inattentive (ADHD-I) [26.9%] subtypes. Patients with ADHD-I were more likely to complete secondary and higher education (p<0.001) and were more qualified for employment (55.2%; p=0.004) relative to the other two subtypes. Despite this, the proportion of patients who never worked was higher among patients with ADHD-I (26.1%; p=0.004) compared with the other ADHD subtypes.
The majority of patients (66.2%) presented with at least one psychiatric comorbidity, and the average number of comorbidities per patient was 2.4. The prevalence of psychiatric disorders was higher in the ADHD-C group relative to the ADHD-I group (72.4% vs 53.6%; p=0.006), but was similar to that in the ADHD-H group (69.6%). The most frequent comorbidities were substance-use disorder (39.2%), anxiety disorder (23.0%), mood disorders (18.1%) and personality disorders (14.2%).
Approximately half of the patients (56.6%) had a history of psychiatric illness among their first-degree relatives, and ADHD was part of this family psychiatric history in 26.9% of the cases. There was no difference in the proportion of patients with a family history of psychiatric conditions or ADHD between the different ADHD subtype groups.
The majority of patients (88.8%) were receiving pharmacological treatment for their ADHD, with modified-release methylphenidate capsules being the most widely used treatment (93.4%). The proportion of patients receiving pharmacological treatment for psychiatric comorbidities was 41.1%.
This study is limited by its cross-sectional design, the retrospective review approach undertaken to examine clinical records, and the lack of limits on selection criteria. Nonetheless, the findings shed light on the high prevalence of concurrent psychiatric illnesses at first-time diagnosis of ADHD, and highlight the importance of mental health centres as favourable settings for efficient ADHD diagnosis, which offers the opportunity for ADHD treatment and mitigation of its negative impact on the patient’s life.
Read more about psychiatric conditions comorbid with adult ADHD here
*Based on the Diagnostic and Statistical Manual of Mental Disorders – 4th edition-Text Revision (DSM-IV-TR)
†Including birth date, sex, marital status, family composition, educational and employment status, and economic level
Piñeiro-Dieguez B, Balanzá-Martínez V, García-García P, et al. Psychiatric comorbidity at the time of diagnosis in adults with ADHD: the CAT study. J Atten Disord 2016; 20: 1066-1075.