Will evening primrose oil help a steenager with moods?

No evidence: I wouldn't rely on evening primrose for your teen's moods. Evening primrose oil is a source of essential omega 6 fatty acid gla. There's some mixed evidence on its efficacy for treating breast pain, menopause & pms. In contrast, omega 3 fatty acids, found in fish oil, show promise in battling mood disorders. Pms may be helped slightly (poor quality data). It may interact w ssri antidepressants.