While drugs like Viagra can certainly help men regain their erections, they won't make them any happier, a new US study claims.

PDE5 inhibitors such as Viagra, which work by relaxing blood vessels, help tackle the physiological side of erectile dysfunction, or ED, but they don't address psychological causes of impotence, LiveScience reports.

The study, which examined 40 clinical trials, was published November 21 in the Journal of Sexual Medicine.

"It's simplistic to think that fixing an erection issue would solve relationship issues," said researcher Dr. Andrew Kramer of the University of Maryland Medical Center. "Happiness is very complicated. A lot of couples still need additional therapy."

Other issues affecting impotence include depression, anxiety, and relationship problems, as well as alcohol and drug use.