Yes, depression and other mood disorders may indeed cause sexual dysfunction. Erections start in the brain and if the brain isn't sending the right signals, sexual problems may occur. Moreover, most antidepressants (e.g. SSRIs) can actually cause or worsen ED.
Alcohol is an interesting case. Large amounts of alcohol inhibit erections but there are studies that show that small amounts can actually improve your sexual performance. I'm not a doctor but I believe that alcohol may activate some of the brain areas that control sexual activity.
Viagra only acts locally but many ED drugs (e.g. apomorphine) work directly in the brain to improve erections. Rexahn Pharmaceuticals is currently developping a new centrally acting ED drug called Zoraxel. Zoraxel shows great promise and should be available in 2013. Another promising new ED drug is bremelanotide (formerly known as PT-141), which is being developped by Palatin.
Hi NJCSTO3,
It sounds like those conditions may be related to the erection issue. I would recommend checking out Emotional Freedom Technique, since that has been know to be HIGHLY effective at treating depression, ADD, and other nervous system disorders. I have personally been using EFT for 3 years now and have seen incredible results.
Best wishes,
Ryan