ADHD, Depression & Anxiety: Overlap, Mechanisms & Integrated Care

ADHD, major depressive disorder (MDD), and anxiety disorders frequently co‑occur. ~30–50% of adults with ADHD have comorbid depression/anxiety; conversely, ADHD is overrepresented in mood/anxiety clinics.

Shared Neurobiology

• Dopamine / norepinephrine dysregulation: central to ADHD; also implicated in reward/motivation deficits in depression and arousal in anxiety.
• Prefrontal‑limbic circuitry: impaired top‑down control (PFC) over amygdala → emotional dysregulation.
• Default mode network (DMN) intrusion: poor task‑related DMN suppression in ADHD; rumination in depression.

Genetic & Environmental Overlap

• Twin studies: shared genetic liability (polygenic risk scores correlate).
• Adverse childhood experiences (ACEs) increase risk for all three.
• Chronic ADHD‑related impairment (academic, occupational, relational) → secondary demoralization, anxiety.

Clinical Implications

• Screen routinely: PHQ‑9, GAD‑7 in ADHD eval; ASRS in mood/anxiety eval.
• Treat the most impairing condition first (often depression/anxiety before ADHD stimulants).
• Stimulants + antidepressants: generally safe; monitor BP/HR, activation.
• Atomoxetine / viloxazine: non‑stimulant options with some anxiety benefit.
• CBT adapted for ADHD: structure, behavioral activation, cognitive restructuring.

Diagnostic Caution

Inattention from depression/anxiety can mimic ADHD. Require childhood onset, cross‑setting impairment, and symptom persistence beyond mood episodes for ADHD diagnosis.