Health and psychological effects
The medical consensus is that masturbation is a medically healthy and psychologically normal habit. According to the Merck Manual of Diagnosis and Therapy, "It is considered abnormal only when it inhibits partner-oriented behavior, is done in public, or is sufficiently compulsive to cause distress."
Masturbation does not produce premature ejaculation.
In the US, masturbation was a diagnosable psychological condition until DSM II (1968). The American Medical Association consensually declared masturbation as normal in 1972.
Sex therapists will sometimes recommend that female patients take time to masturbate to orgasm, for example to help improve sexual health and relationships, to help determine what is erotically pleasing to them, and because mutual masturbation can lead to more satisfying sexual relationships and added intimacy.
It is held in many mental health circles that masturbation can relieve depression and lead to a higher sense of self-esteem. Masturbation can also be particularly useful in relationships where one partner wants more sex than the other – in which case masturbation provides a balancing effect and thus a more harmonious relationship.
Mutual masturbation, the act by which two or more partners stimulate themselves in the presence of each other, allows a couple to reveal the "map to [their] pleasure centers". By watching a partner masturbate, one finds out the methods they use to please him- or herself, allowing each partner to learn exactly how the other enjoys being touched. Intercourse, by itself, is often inconvenient or impractical at times to provide sufficient sexual release for many people. Mutual masturbation allows couples to enjoy each other and obtain sexual release as often as they need but without the inconveniences and risks associated with sex.
In 2003, an Australian research team led by Graham Giles of The Cancer Council Australia found that males masturbating frequently had a lower probability to develop prostate cancer. Men who averaged five or more ejaculations weekly in their 20s had significantly lower risk. However they could not show a direct causation. The study also indicated that increased ejaculation through masturbation rather than intercourse would be more helpful as intercourse is associated with diseases (STDs) that may increase the risk of cancer instead. However, this benefit may be age related. A 2008 study concluded that frequent ejaculation between the ages of 20 and 40 may be correlated with higher risk of developing prostate cancer. On the other hand, frequent ejaculation in one's 50s was found to be correlated with a lower such risk in this same study.
A study published in 1997 found an inverse association between death from coronary heart disease and frequency of orgasm even given the risk that myocardial ischaemia and myocardial infarction can be triggered by sexual activity.
The association between frequency of orgasm and all cause mortality was also examined using the midpoint of each response category recorded as number of orgasms per year. The age adjusted odds ratio for an increase of 100 orgasms per year was 0.64 (0.44 to 0.95).
That is, a difference in mortality appeared between any two subjects when one subject ejaculated at around two times per week more than the other. Assuming a broad range average of between 3 and 5 ejaculations per week for healthy males, this would mean 5 to 7 ejaculations per week. This is consistent with a 2003 Australia article on the benefits against prostate cancer. The strength of these correlations increased with increasing frequency of ejaculation.
A 2008 study at Tabriz Medical University found ejaculation reduces swollen nasal blood vessels, freeing the airway for normal breathing. The mechanism is through stimulation of the sympathetic nervous system and is long lasting. The study author suggests "It can be done [from] time-to-time to alleviate the congestion and the patient can adjust the number of intercourses or masturbations depending on the severity of the symptoms."
Solo masturbation is a sexual activity that is free of risk of sexually transmitted infections. With two or more participants, the risk of sexually transmitted infections, while not eliminated, is much less than with most forms of penetrative sex. Support for such a view, and for making masturbation part of the American sex education curriculum, led to the dismissal of US Surgeon General Joycelyn Elders during the Clinton administration. Some EU Nations promote masturbation in their sex education curricula.
Sexual climax, from masturbation or otherwise, leaves one in a relaxed and contented state. This is frequently followed closely by drowsiness and sleep – particularly when one masturbates in bed.
Some professionals consider masturbation to function as a cardiovascular workout. Though research is still as yet scant, those suffering from cardiovascular disorders (particularly those recovering from myocardial infarction, or heart attacks) should resume physical activity (including sexual intercourse and masturbation) gradually and with the frequency and rigor which their physical status will allow. This limitation can serve as encouragement to follow through with physical therapy sessions to help improve endurance. In general, real sex slightly increases energy consumption, according to a study published in the New England Journal of Medicine.
Both sex and masturbation lower blood pressure. A small study demonstrated lower blood pressure in persons who had recently masturbated compared to those with no proximate sexual activity.
Those who insert objects as aids to masturbation risk them becoming stuck (e.g. as rectal foreign bodies). Men and women can fall prey to this problem. A woman went into a German hospital with two pencils in her bladder, having pierced her urethra after inserting them during masturbation.
Solo masturbation, or masturbation involving individuals of the same sex, cannot produce pregnancy. Masturbation involving both a man and a woman (see mutual masturbation) can result in pregnancy only if semen contacts the vulva.
Problems for males
A man whose penis has suffered a blunt trauma, severe bend or other injury during intercourse or masturbation may, rarely, sustain a penile fracture or suffer from Peyronie's disease. Phimosis is "a contracted foreskin (that) may cause trouble by hurting when an attempt is made to pull the foreskin back". In these cases, any energetic manipulation of the penis can be problematic.
A small percentage of men suffer from postorgasmic illness syndrome (POIS), which can cause severe muscle pain throughout the body and other symptoms immediately following ejaculation, whether due to masturbation or partnered sex. The symptoms last for up to a week. Some doctors speculate that the frequency of POIS "in the population may be greater than has been reported in the academic literature", and that many POIS sufferers are undiagnosed.
Compulsive masturbation and other compulsive behaviors can be signs of an emotional problem, which may need to be addressed by a mental health specialist. As with any "nervous habit", it is more helpful to consider the causes of compulsive behavior, rather than try to repress masturbation.
Masturbation among adolescents contributes to them developing a sense of mastery over sexual impulses, and it has a role in the physical and emotional development of prepubescents and pubescents. Babies and toddlers will play with their genitals in much the same way as they play with their ears or toes. If such play becomes all-consuming, it may be necessary to look for an underlying cause of this, such as the child being tense and in need of comfort, or that others may be overreacting and thus reinforcing the habit. It could be caused by a low-grade urinary tract or yeast infection, or the child may be overstimulated and in need of soothing, or indeed understimulated and bored. Alongside many other factors, such as medical evidence, age-inappropriate sexual knowledge, sexualized play or aggression, and precocious or seductive behavior, excessive masturbation may alternatively be an indicator of sexual abuse.