Semen is good for women's mental and physical health, a new study claims.Seminal fluid contains at least three anti-depressants as well as mood-altering chemicals which increase affection and induce sleep.Researchers also claim that women who have regular unprotected sex are less depressed and perform better on cognitive tests.The State University of New York survey examined the sex lives and mental health of 293 females.Seminal fluid contains other chemicals beside sperm – including estrone and oxytocin, which elevates mood, and cortisol, which is known to increase affection.It also contains the antidepressant thyrotropin-releasing hormone, sleep-inducing melatonin and well-known mood-booster serotonin.Researchers Gallup and Burch, along with the psychologist Steven Platek, hypothesised that women having unprotected sex should be less depressed than others due to human semen’s mind-altering 'drugs'.They rounded up 293 college females from the university's Albany campus and gave them an anonymous questionnaire about their sex lives.Recent sexual activity without condoms was used as an indirect measure of seminal plasma circulating in the woman’s body.Participants also completed the Beck Depression Inventory, a commonly used clinical measure of depressive symptoms.The study, published in the Archives of Sexual Behaviour, showed that women who engaged in sex and “never” used condoms showed significantly fewer depressive symptoms than did those who “usually” or “always” used condoms.The non-condom-using, sexually active women also showed fewer depressive symptoms than those who abstained from sex altogether.Meanwhile, sexually-active and “promiscuous” heterosexual women who used condoms were just as depressed as those practising total abstinence.Researchers propose that happiness among sexually-active women appears to be a function of semen’s chemicals pulsing through body.