Do you know anyone with obsessive compulsive disorder where they need to do actions repeatedly?
Not personally, but I've heard about it.  Do you have it?
No I don't. People are unable to control their thoughts or activities more than a short time.
Is it psychological or biochemical?
Good question. The cause actually is unknown. Some people think child abuse or a stressful event could play a role.
Can it be treated with therapy?  Or chemically?
Many sufferers to seek therapy from psychologists. The rating scale such as Yale Brown Obsessive Compulsive Scale helps with diagnosis.
It's easy to see how it could negatively effect a person's life!
True and the diagnosis is based on symptoms and requires ruling out other causes.
How effective is the treatment?