According to a study published in the Journal of Male Reproductive Physiology (Andrologia), sub-chronic psychological stress can affect male fertility. The study conducted by researchers from BHU Central University revealed that a global crisis in male reproduction is indicated by a decline in sperm count and an increased rate of abnormalities in the male reproductive system. Over time, multiple studies have revealed that a modified lifestyle, including stress, nutrition, coffee intake, physical activity, diet, and a high scrotal temperature, has led to infertility and impotency.

In this study, the researchers exposed study subjects to sub-chronic stress for 1.5–3 hours every day for 30 days. They measured the quality and quantity of sperm after 30 days. The findings of the study showed that the subjects who were exposed to stress developed symptoms that could lead to infertility.

They also found that in most of the subjects, there was a severe deterioration in daily sperm count and production. They also found morphological and structural abnormalities in the sperm, especially the epididymal spermatozoa. They found that in a majority of the cases, the sperm had a higher number of tail abnormalities in comparison to head abnormalities, which adversely affected their motility.

Additionally, they also found that the stress disrupted male hormone synthesis, which in turn increased the oxidative stress in the testis. 

(Source: https://health.economictimes.indiatimes.com/news/diagnostics/sub-chronic-psychological-stress-affects-male-fertility/96796792 )