Direct human evidence on male masturbation as a health or fertility practice is limited. Primate data show an evolutionary pattern: masturbation is an ancient trait, and it became more common in haplorrhines after the split from tarsiers. In men, the available findings are observational associations, mainly with sperm quality and prostate cancer risk. The link with sexual satisfaction is correlational and its direction is unknown: in most studies of men, solitary masturbation accompanied lower satisfaction. No source reviewed here isolates masturbation alone or proves that it causes any of these outcomes.
The question matters because claims about ejaculation, fertility and cancer risk circulate widely, and separating what was measured from what is assumed lets readers judge them for themselves.
What does evolution say about masturbation in primates?
The Brindle et al. 2023 analysis in Proceedings of the Royal Society B used phylogenetic comparative methods across the primate order and found that masturbation is an ancient trait, more common in haplorrhines after the split from tarsiers. The authors interpret this pattern as compatible with adaptive explanations, though the study measured species-level patterns, not individual human fertility.
Direct human evidence on masturbation and fertility is limited and mostly observational. — Image: AI-generated / Gemini 3.1 Flash via OpenRouter
The analyses support the Postcopulatory Selection Hypothesis, in which masturbation improves the chance of fertilization, and the Pathogen Avoidance Hypothesis, in which masturbation reduces infection by flushing pathogens from the genital tract in male primates. This suggests that masturbation may be an adaptive trait at a macroevolutionary scale. The limitation is that the unit of analysis is the species; the study did not measure sperm quality, infection or fertility in individual humans.
For human fertility or infection, the evolutionary argument remains indirect. [More research needed: none of the sources reviewed for this article was a randomized trial testing the effect of masturbation alone on fertility or infection in men.]
How is ejaculation frequency linked to sperm quality?
In the Xi et al. 2025 cross-sectional study of 1,349 men who had semen analysis at a reproductive centre, higher self-reported ejaculation frequency over the previous 4 weeks was associated with lower sperm DNA fragmentation index, lower semen volume, lower sperm concentration and lower total sperm count, while sperm vitality increased.
The study grouped men by fewer than 1 ejaculation per week, 1 or more but fewer than 2 per week, and 2 or more per week. The 2 higher-frequency groups had lower risk of elevated DNA fragmentation index and of necrozoospermia, with no increased risk of oligozoospermia or asthenozoospermia. Progressive motility showed no association. Because the design is cross-sectional and the men were attending a fertility centre, causation cannot be shown, and ejaculation frequency includes partnered sex rather than masturbation alone.
The pattern is therefore mixed rather than uniformly favorable: lower DNA fragmentation index and higher vitality appear alongside lower semen volume, sperm concentration and total sperm count.
How is ejaculation frequency linked to prostate cancer risk?
In the Rider et al. 2016 prospective cohort of 31,925 men followed to 2010, 3,839 were diagnosed with prostate cancer. A frequency of 21 or more ejaculations per month was associated with lower prostate cancer risk than 4 to 7 ejaculations per month, with a hazard ratio of 0.81 (95% CI 0.72 to 0.92) at ages 20 to 29.
For frequency at ages 40 to 49, the hazard ratio was 0.78 (95% CI 0.69 to 0.89). The association was driven by low-risk disease. The study is observational, exposure was self-reported, ejaculation was by any route rather than masturbation alone, and the findings cannot support a conclusion that more ejaculation causes lower risk.
The hazard ratios describe diagnosed prostate cancer across a large cohort, not one man’s prognosis.
How is masturbation linked to men’s sexual satisfaction?
In the Cervilla et al. 2024 systematic review of 22 articles on solitary masturbation and sexual satisfaction, 71.4% of studies in men found a negative relation, 21.4% found no relation and 7.2% found a positive relation. The authors interpret this pattern as consistent with a compensatory role of masturbation, especially in men.
In women, 40% of studies found no relation, 33.3% found a negative relation and 26.7% found a positive relation, which makes the male pattern less uniform than it appears. The relation is correlational, and its direction of causation is unknown: lower satisfaction may prompt more solitary masturbation, or more solitary masturbation may accompany lower satisfaction.
In clinical work with men, a recurring pattern is that worry about the number of times comes up more than any specific figure from the evidence; the clinical yardstick is harm to work, relationships and mood, not counting.
No direct human evidence in the sources reviewed shows that masturbation improves fertility. The Brindle et al. 2023 primate analysis supports the Postcopulatory Selection Hypothesis at a species level, not in individual men. The Xi et al. 2025 cross-sectional study found mixed associations with semen parameters, not fertility.
Does masturbation reduce the risk of sexually transmitted infections?
No direct human evidence in the sources reviewed shows that masturbation reduces the risk of sexually transmitted infections. The Pathogen Avoidance Hypothesis proposes that masturbation reduces infection by flushing pathogens from the genital tract in male primates, and the Brindle et al. 2023 analysis supports it only in primates.
How many ejaculations per month are healthy?
The studies reviewed here give no recommended number of ejaculations per month. The Rider et al. 2016 cohort only compared categories, such as 21 or more ejaculations per month versus 4 to 7 per month. No healthy count can be derived from these data.
Does masturbation reduce sexual satisfaction?
The Cervilla et al. 2024 systematic review of 22 articles found that 71.4% of studies in men reported a negative relation between solitary masturbation and sexual satisfaction, while 21.4% found no relation and 7.2% found a positive relation. The relation is correlational.
What the Evidence Says and Does Not Say
Our editorial position is that masturbation is a common, normal sexual behaviour and its worth should not be judged by a single number or a claimed benefit; what these studies support is only a set of limited associations.
Better-designed studies can clarify which associations are real. Until then, the evidence on male masturbation is best summarized as limited, observational and, for some outcomes, mixed, and nothing in it calls for worry or for a counting routine.
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Brindle M, Ferguson-Gow H, Williamson J, Thomsen R, Sommer V. The evolution of masturbation is associated with postcopulatory selection and pathogen avoidance in primates. Proc Biol Sci. 2023;290(2000):20230061. PMID: 37282530. DOI: 10.1098/rspb.2023.0061
Xi Q, Kong Q, Lv X, Dai R, Yu Y. Impact of ejaculation frequency on semen parameters and DNA fragmentation: a cross-sectional study. Reprod Biol Endocrinol. 2025;23(1):100. PMID: 40671092. DOI: 10.1186/s12958-025-01439-3
Rider JR, Wilson KM, Sinnott JA, Kelly RS, Mucci LA, Giovannucci EL. Ejaculation Frequency and Risk of Prostate Cancer: Updated Results with an Additional Decade of Follow-up. Eur Urol. 2016;70(6):974-982. PMID: 27033442. DOI: 10.1016/j.eururo.2016.03.027
Cervilla O, Álvarez-Muelas A, Sierra JC. Relationship between Solitary Masturbation and Sexual Satisfaction: A Systematic Review. Healthcare (Basel). 2024;12(2):235. PMID: 38255122. DOI: 10.3390/healthcare12020235
Image credits: the featured image and the first in-text image are AI-generated (Gemini 3.1 Flash via OpenRouter).
