I know why - and it is a dirty secret. The drug class known as "SSRI's" have a rare but incomprehensible side affect. They can cause suicidal "rage" - no note, no planning, etc...just - "hey, this is what I need to do - NOW" Some sublimate the suicide rage into homicidal rage - and the rage tones done as the planning phase is executed, and then comes right back with conviction. These people "know" that this has to be done while at the same time knowing that it is wrong. The drug gives them the power to rise above this conflict and act out. I know these drugs have helped millions of people, so don't take personal offense. I agree they do a lot of good. But people need to know this about these drugs. Think about it - a drug to make people happy should benefit the entire population - "Thanks! Have a Great Day!" These drugs don't make the cashier at walmart any more friendly, but they could send him into homocidal rage.