Cause

A woman's lack of sexual interest is often tied to her relationship with her partner, says Sandra Lieblum, director for sexual and marital health at the UMDNJ Robert Wood Johnson Medical School in Piscataway, N.J. "The important sex organ [for women] is between the ears. Men need a place for having sex — women need a purpose," she says. But it can also be triggered by family concerns, illness or death, financial or job worries, childcare responsibilities, managing a career and children, previous or current physical and emotional abuse, fatigue and depression.

Indeed, female sexual dysfunction seems to be psychologically — rather than physically — rooted. "What the genitals are doing may play a less important role in how a woman defines her sexual arousal," says Meston. "I don't think there will ever be an aphrodisiac that will make [women] want to have sex all the time."

That's not to say its causes aren't physical, Lieblum says. Hypertension, heart disease, cancer, diabetes, thyroid disorders, neurological diseases and autoimmune disorders like lupus can all contribute to a woman's lack of sexual desire. Other factors include prescriptions drugs, particularly anti-hypertensives and depression medication, as well as over-the-counter medications and illegal drugs and alcohol abuse.