“Use it or lose it” has a pretty broad applicability to the entire body. If you don’t use your muscles, strength or flexibility, they’ll eventually dissipate from having not been worked enough. Your penis can function under the same axiom. You’re not going to actually lose it if you don’t use it — it won’t fall off or anything — but it can indeed atrophy after periods of abandonment. That is, it can both lose its abilities and become smaller. At least, kind of.
The most common cause of penis atrophy or shrinkage is simply the result of aging. As men get older, reduced blood flow and weakened muscle cells lead to a reduced capacity to hold an erection, as well as a less-firm erection overall. Rather than the penis actually becoming smaller, it’s more akin to a pool floaty without enough air inside of it — the pool floaty is technically the same size, it’s just not as full as it once was. However, there is some speculation that a decrease in healthy penile tissue also occurs with aging, as well.
Considering that other causes of erectile dysfunction, such as high blood pressure or cardiovascular problems, also correlate with aging, “not using it” as the result of erectile dysfunction could indeed coincide with this decrease in size. As such, penis atrophy is far more likely to be the result of issues beyond simply not becoming erect by choice.
For a young and healthy individual who simply abstains from sex and masturbation, even if they somehow manage to avoid becoming erect entirely, it’s unlikely that they’ll have any long-term type of atrophy. An older but still healthy individual with this lifestyle may indeed experience atrophy in the form of shrinkage, but they won’t likely lose functionality just because they haven’t been using their penis.
Other common forms of penis atrophy might technically be linked to not using one’s penis, too, but there’s typically a much more significant cause that’s responsible. For example, one 2008 study in the International Journal of Impotence Research found that 71 percent of men who underwent radical retropubic prostatectomy experienced at least mild penile shrinkage. This surgery can also cause a temporary lack of function. Without proper care, this lack of function can persist. Though one’s size won’t likely ever return to normal, there is indeed penile physical therapy for men who’ve had prostate surgery to help regain function.
Weight gain, cigarette smoking and certain medications like Adderall and antidepressants have also been linked to shrinkage, though this is typically reversible. Weight gain causes shrinkage by essentially pulling the shaft of the penis further into the body, while cigarettes and medications can impede blood flow. Losing weight, ceasing smoking and discontinuing medications usually bring blood flow back to normal.
Overall, most cases of penis atrophy are self-cyclical. Something happens that impedes penile function, you stop using it and that impediment continues. It might seem like it has atrophied from going ignored, but there is probably a correlated cause at play.