Certain head and neck cancers may be tied to sexual activity, marijuana use, and human papillomavirus (HPV ) type 16.

That news comes from Johns Hopkins University’s Maura Gillison, MD, PhD, and colleagues, who studied 240 people with head and neck squamous cell carcinomas (head and neck cancers). Some of their cancers tested positive for HPV 16; others were negative for HPV 16.

The patients answered questions about their lifestyle. For comparison, 322 cancer-free people answered the same lifestyle questions.

Here’s what the researchers learned: