Leading psychosexual therapist Angela Gregory said an increasing number of men in their late teens and early 20s are suffering from erectile dysfunction as a result of becoming addicted to watching porn on the internet.
While there are no official figures, Gregory believes that young people are predominantly watching porn on their smartphones and laptops.
"What I've seen over the last 16 years, particularly the last five years, is an increase in the amount of younger men being referred," she told BBC Newsbeat.
"Our experience is that historically men that were referred to our clinic with problems with erectile dysfunction were older men whose issues were related to diabetes, MS, cardio vascular disease.
"These younger men do not have organic disease, they've already been tested by their GP and everything is fine.
"So one of the first assessment questions I'd always ask now is about pornography and masturbatory habit because that can be the cause of their issues about maintaining an erection with a partner."
Anyone who is concerned that they may have a problem related to porn should speak to their local GP, Gregory advised.