Almost certainly not ADHD. "Massively increased appetite" is not a typical side effect of ADHD meds, which are typically stimulants which have the opposite effect (and mine give me nausea on top of that). And "drowsiness and brain fog" are what they're trying to combat.

From the complaints I've heard from friends, those sound like pretty typical side effects for SSRIs. (Bupropion OTOH is both a stimulant and an antidepressant, and may be more effective for people with comorbidity ADHD and depression; the POV character should talk to their psychiatrist)