Parents can spot a questionable friend group from three counties away. Young adults, inconveniently, still get to form their own conclusions.

Peers matter—but avoid declaring that one friend “caused” anxiety, depression or risky behavior. A 2026 Finnish cohort study followed 604,819 people and found that peer environments were associated with later mental-health trajectories. For example, peer genetic risk for externalizing disorders in upper-secondary school was associated with a 34% higher relative risk of the same category of diagnosis. The researchers emphasized that mechanisms remain unclear; people also select friends who resemble them.

Look for change rather than disapproval: disrupted sleep, falling grades, constant crises, isolation from old supports, substance use, humiliating jokes, financial pressure or fear of disagreeing with the group.

Lead with observation. “You seem anxious after spending time with them” lands better than “Those people are bad news.” Ask what your young adult enjoys, what feels hard and whether they can say no without punishment.

Keep home emotionally safe enough that honesty does not require defending every friend. A parent who insults the group may accidentally make the group the only place left to belong.

Influence is real. So is autonomy. The goal is not to choose their friends; it is to help them notice what each friendship draws out of them.

Research: Nationwide cohort study of peer environments and later mental-health risk

Related reading: How to Make Your Home Emotionally Safe for Your Young Adult’s Honesty

This article provides general educational information and is not a substitute for individualized mental-health, medical or legal advice.