OBJECTIVE: To study the associations between self-reported psychological stress, semen quality, and serum reproductive hormones among young Danish men.

DESIGN: Cross-sectional study.

SETTING: University hospital-based research center.

PARTICIPANT(S): Danish men (median age 19 years) from the general population were investigated from 2008 to 2012.

INTERVENTION(S): Participants completed a questionnaire on health and lifestyle, including a four-item questionnaire about self-rated stress, had a physical examination performed, delivered a semen sample, and had a blood sample drawn.

MAIN OUTCOME MEASURE(S): Semen parameters (semen volume, sperm concentration, and percentages of motile and morphologically normal spermatozoa) and serum levels of reproductive hormones (LH, FSH, T, calculated free T, sex hormone-binding globulin, and inhibin B).

RESULT(S): Poorer semen quality was detected among men with self-reported stress scores above an intermediate stress level, in a dose-response manner. For example, men with the highest stress levels had 38% (95% confidence interval [CI] 3%; 61%) lower sperm concentration, 34% (95% CI 59%; 106%) lower total sperm count, and 15% (95% CI 1%; 27%) lower semen volume than men with intermediate stress levels. No significant associations between self-reported stress and levels of reproductive hormones were detected.

CONCLUSION(S): A negative association between self-reported stress and semen quality was detected. If causal, stress may be a contributing factor for suboptimal semen quality among otherwise healthy men.