Hi, thanks for using healthcare magic
Reduction in semen volume can be due to:(1) psychological reasons (2) short abstinence period (3) retrograde ejaculation
(the semen goes in the wrong direction) (4) blockage of the ejaculatory duct
(5) decrease in testosterone
(6) problems or disease of the seminal vesicle
which make the majority of the ejaculate.The seminal vesicle are glands located near the bladder
The psychological stress that your friend is experiencing and his weight (excess weight is associated with hypogonadism which is when the sex glands produce little or no sex hormones such as testosterone) may be contributing to his problem.
Your friend should consult a urologist
who will be able to investigate him appropiately.
I hope this helps