I agree with Kat. There is at least one sleeping position which NEVER fails to "put H in the mood," but while he was going through his most depressed phase ... nothing. There literally wasn't enough seratonin in his brain to transmit any impulses. I think this is very difficult for a person who has never experienced moderate to severe depression to understand, however.
Kalni, my deepest sympathies for what your family is going through with your Dad's condition right now.