not a classical case of BP he could have been dx OCD say, but underneath traits of BP so he will have had minor
bipolar symptoms going back years, as many with late-onset
bipolar do. Antidepressants or other meds initiate a permanent change in symptoms, causing them to become more extreme and cross the threshold into diagnosable - or clinical - bipolar disorder.
Some meds can do the above, and others can cause short-term bipolar
symptoms in some people.