Undetected ADHD as a Predictor of Treatment-Resistant Generalized Anxiety Disorder in a Clinical Population

The co-occurrence of attention deficit hyperactivity disorder (ADHD) and generalized anxiety disorder (GAD) is common. Comorbid ADHD has been associated with treatment-resistance and poorer outcomes in depressed adults prescribed selective serotonin reuptake inhibitors (SSRIs). Little is known about the influence of comorbid ADHD on treatment response in patients with GAD. The aim of this study was to assess the prevalence of ADHD in a referred sample and identify predictive factors of treatment-resistance in those that met criteria of comorbid GAD and ADHD.

Data from consecutive referrals (N = 97) to a tertiary-care psychiatric clinic was assessed for reason for referral, primary diagnosis, number of diagnoses, and medication history. Diagnosis was established using the MINI International Neuropsychiatric Interview Plus 6.0.0 and semi-structured psychiatric assessment. Statistical analysis was conducted to examine factors and clinical features associated with undiagnosed ADHD and treatment-resistance.

ADHD was present in 34% of referrals, 39.2% of GAD, and 45.6% of treatment-resistant GAD cases. The number of psychiatric diagnoses (p < .001), past SSRI failure (p < .039), and number of SSRI failures (p < .038) were predictive of undetected ADHD. Undiagnosed ADHD (p = .023), social phobia (p = .015), and number of referral diagnoses (p < .001) significantly predicted treatment-resistant GAD.

These results demonstrated ADHD is often unrecognized in adults referred for the treatment of GAD. Moreover, multiple diagnoses and past SSRI failure are indicative of treatment-resistance referral diagnoses. This signifies the importance of screening for ADHD in all adult GAD patients presenting with treatment-resistance.