It's good that you wrote.
I was about 27 when my bi-polar struck.
But at 17, I had a psychotic episode, which was probably the break out of my bi-polar, for after that, I was from time to time taking tranquilizers, nervous in certain situations.
So it would have been attached to something, it turns out probably bi-polar, but I didn't know that. At 27, I was unemployed, little socialization for a few weeks, and stared getting depressed with a few days of being unemployed.
Did not get the depression treated, and after 3 or 4 weeks of depression, it felt like a heavy weight on my head that was not being taken away, and I collapsed into a nervous breakdown.
Really, got no diagnosis after that, and then, a few years later diagnosed as just depressed, which can happen when patients are seen in the depressed state.
Any questions about mania are often not asked, so it's good that your son got diagnosed correctly at 18, a year ago.
If not diagnosed correctly, they can't medicate right, so the diagnosis is very important. To see if you think it might be bipolar, you might check on the web and look at the symptoms.
Is he still in school? How is he dealing with all of this? Does he take his meds? He is also entering the age when he will want to go to parties, and alcohol could very possibly conflict with his medicines. So, we don't know what's going to happen there.
Was he doing OK, and then he started doing not OK?
I take Lithium (675 mg., a day) and Mirtazapine (7.5 mg.) anti-depressant (which I think is generic of Rimmiron [sp?].
It's good that he has people helping him. Please let us know how he is doing.