Well, supposedly she had been diagnosed with bipolar disorder. This is a specific disease and is not necessarily brought on by stress, but a bout of it can be. There is the manic phase and the depressive phase, and the depression of BPD is particularly dark.
And I think that if he had dealt with his real issues and gotten the right advice years ago he would have been off the drugs by now.
Yes, it's tough but too much enablement makes it way tougher IMO.