SSRI's, SRNI's, TCA's, Buproprion, and all other mood altering drugs, seizure medications, alcohol, marijuana, sleeping medications, steroids (anabolic and corticosteroid), and many, many, many more, can really lead to unpredictable situations. Luckily, severe issues don't happen to often, but lesser ones happen all the time, like impulse control issues, mild memory loss, etc.
I work in the field (no, it didn't keep my wife from cheating on me and I didn't understand what was happening at the time because she didn't want to talk about her treatment and her med dose had been increased...of a very common antidepressant), but I've treated a lot of people and heard every story you can imagine, from people having little or no memory of long periods of time (I've personally treated someone who was out of it for 2 months and was hospitalized until his brain function normalized and he realized where he was,luckily I wasn't the prescriber).
I recently treated someone who was convinced that they had won something, and was trying to claim it, caused by Prednisone, this person had to be hospitalized and placed in a residential facility with locked doors for nearly a month, until the delusion cleared, which is where they met me.
I had no idea that some day I was going to live my work.
Character/Personality changes, it happened to my wife when she was placed on an antidepressant and her change was that she wanted me to leave, actually wanted me to die, and while I was doing both of those things she wanted me to hurt as much as possible.
She remembers very little of that time, but she remembers how much she wanted me to hurt, how badly she wanted me to hurt, and how she was willing to do anything to make it happen, and she did what she knew to do, which was have sex with someone else, take the kids to meet him, and then....wham...she was suddenly "what the hell am I doing, why am I doing this".
In her case, her anger, long suppressed, largely hidden and never talked about, came unbound.
We had been married for 9 years and I had no clue what the truth was about her childhood. This despite the fact that we lived in the area where she grew up and I knew both her mother and father and sister and stepsisters and stepmother and stepfather. Because nobody talked about the truth.
Her anger was with her father and mother and how they didn't protect her and her sister from the abuse they suffered.
The antidepressants caused that anger to come out in a vicious and uncontrolled manner (seriously, she actually remembers really hoping I'd get killed in an accident on the way home and has been terribly ashamed of that since this all happened 12 years ago this month and she has remembered it every year and every year this month is pretty terrible and around 3 years ago I finally found out why) and it was all directed at me, not the father and mother.
Why? Was I an asshole? No.
Even she says that she doesn't understand why she became so angry at me. She's been the kindest and friendliest person that I think I've ever known (she's got codependency issues). But not then, and I've never known her to treat anyone remotely like she treated me when this happened, which was why it was so difficult to understand. She lied about her childhood and life and the affair all the way up to 7 months into counseling. Then, it became apparent that I was going to leave because she just couldn't get the story she was telling to make sense,to many holes in it.
Then, the truth started to come out, and it became a flood, and it was not pretty.
Did the antidepressants cause her affair?
No, but they caused her to lose control of her anger, and she had a lot of suppressed anger. It was like uncorking a bottle of champagne on a hot day.
Then, the family history played out again, but this time in our marriage...in her family if you got mad at your spouse, you went and fucked someone else, and if both spouses were mad at each other, then that meant that both were out fucking other people and the children were left to fend for themselves...and at least one of the people they had to fend with was a child sex abuser.