I'm bipolar, schizoaffective, & have PTSD as well (hell of a combo, I know), & I can understand why he would resort to such measures. Robin was bipolar (from what I've heard), & had just been diagnosed as having Parkinson's (an even worse combo)... Who knows what went through his mind before he took his own life? Maybe he felt that it was all too much to deal w/?
I'm not excusing or condoning what he did, I'm just saying that it's understandable. I remember having suicidal thoughts in my early twenties (due to the PTSD), yet I never followed through w/ it (attempted once, changed my mind at the last second). It's sad that he felt that this was the only way to deal &/or end his issues.