Single people who take antidepressants such as Prozac and Zoloft may be depressing their chances of falling in love, according to a new theory. Biological anthropologist Helen Fisher and psychiatrist James Thomson, who specialize in studies of romantic attachment, say they’ve seen evidence that antidepressants alter brain chemistry in a way that minimizes the chance a person can fall in love or feel strong romantic attachment. Antidepressants called SSRIs (selective serotonin reuptake inhibitors) lift mood by increasing the concentration of serotonin between nerves in the brain. But SSRIs also decrease levels of dopamine, a pleasure chemical that has a key role in the brain’s love and sex pathways. Research has shown that these medications suppress sexual desire in many people, and a recent study found that they even led women to rate photos of handsome men as less attractive. Thomson believes that there are many antidepressant users out there whose feelings for new dates or for long-term lovers have been dulled by their pills. “There are all sorts of unconscious systems in our brain that we use to negotiate romantic love and romantic attraction,” Thomson tells “If these drugs cause conscious sexual side effects, we’d argue that there are going to be side effects that are not conscious.”