Viagra

Erections are about blood to the penis. I have diabetes, which constricts blood flow. More recently I have developed hyper-tension, which further screws up blood circulation. And I have depression which has some sexual effects.

All-in-all that's not a good combination.

I've discovered that there's a small subset of men with ED who are resistant to Viagra, primarily those with a combination of diabetes, hypertension, and depression.

Sigh. That's a developement that's really helpful in controlling depression.

Update:
An interesting post on the precursers to Viagra