One of the most common treatable cause of the inability to have an orgasm or decreased interest in sex is depression. Mood and sex have similar hormonal pathways in the brain, so sex really starts in the brain. The imbalance in the hormones that cause depression in the brain also cause decreased libido and desire for sex. Also, some antidepressant medication can cause sexual dysfunction even though they help the mood.
In the evaluation of sexual dysfunction open communication with partner and treating physician is important. It is critical to find out if depression is the case of the sexual dysfunction or the medications a person is on. By changing medications and adding natural and herbal supplements in most cases improvement in both depression and sexual dysfunction can result.