Evening primrose oil for mood swings: what the trials found

Evening primrose oil (EPO) is a plant oil high in gamma-linolenic acid, not a hormone, so it works differently from hormonal medications. There's no trial evidence that it causes depression, anxiety, or mood swings as a side effect.

People often reach for EPO because it's marketed broadly for premenstrual symptoms, including breast tenderness and bloating, not because trials have shown it helps mood specifically. The side effects most often reported are mild:

• Nausea
• Headache
• Loose stools

A 2024 systematic review of EPO across several health conditions found it didn't show effectiveness for premenstrual syndrome, but it also didn't flag new mood symptoms as a risk.

If a mood change showed up after you started taking it, it's worth checking whether the timing matches your cycle rather than the supplement. Evening primrose oil side effects covers what else people notice, including the physical ones.

The best evidence so far says no, not reliably. A small double-blind crossover trial gave women with PMS-related nervous symptoms either EPO (as Efamol and Efavit) or placebo for two months each. The trial:

• Started by screening 24 women with PMS
• Narrowed to 12 whose symptoms were limited to the days before their period
• Had 10 women complete both treatment arms

Depression and anxiety scores improved during the medication months, but they improved just as much during the placebo months. There was no real difference between the two. That 2024 systematic review found the same pattern more broadly. It reported no effect for premenstrual syndrome, which includes the mood symptoms that come with it.

Your anxiety or low mood before your period is still real. This particular supplement just hasn't shown a measurable effect beyond what a placebo gives you in the available trial. Evening primrose oil for PMS walks through what the research does and doesn't support.

Hormonal contraception works differently than EPO. Instead of adding a plant oil, it changes the hormones your body makes or how steady they stay across your cycle.

PMDD is a different reaction to normal hormone changes, not a result of abnormal hormone levels. That's part of why some people on hormonal contraception notice their mood settle, and others notice new mood symptoms. The same shift in hormones can land differently in different brains.

This is a separate question from whether EPO helps your mood, since EPO doesn't change your hormones at all. If you're weighing hormonal contraception against a non-hormonal option like EPO, a doctor can help you match the choice to your history and symptoms.

There's no established timeline here, because no trial found that EPO affects mood in either direction. The physical side effects it can cause, like nausea or a headache, are usually mild and tend to ease without needing to stop the supplement, per the 2024 systematic review of EPO across several conditions.

If a mood change shows up and tracks with your cycle rather than with when you started or stopped EPO, that pattern points to hormones, not the oil. Tracking your mood alongside your cycle for a cycle or two can help you tell the difference. Evening primrose oil dosage covers how it's typically taken.

The trial evidence doesn't point that way either. The one placebo-controlled trial on EPO for PMS-related nervous symptoms found no benefit over placebo, and it wasn't designed around a PMDD diagnosis specifically. The 2024 systematic review found the same lack of effect for PMS more broadly.

EPO is often marketed on the idea that an imbalance in certain fatty acids contributes to premenstrual symptoms, including mood, but that idea hasn't translated into a measured benefit in the trial available.

A different supplement, inositol, has shown more promise for PMDD mood symptoms specifically. A meta-analysis pooling two PMDD trials found a trend toward inositol helping depressive symptoms, though the result sat just short of standard significance (p = 0.07), so the evidence is still preliminary.

If PMDD is what you're dealing with, evening primrose oil for PMDD covers why the condition responds differently to treatment than typical PMS, and PMS supplements lays out what else has been studied.

Evening primrose oil isn't the option with the strongest evidence for premenstrual mood symptoms. A few approaches have more support behind them.

A doctor can also talk through:

• SSRIs, which some people take only in the two weeks before their period rather than every day
• Certain hormonal contraceptives

Guidelines list both as options for more severe premenstrual mood symptoms, with a doctor deciding what fits.

If you want somewhere to put a hard moment while you sort out what helps long term, Niyora is a PMS and PMDD support app. Its Moon feature lets you write down what happened, see it from another angle, and draft a reply you can hold onto before you send anything.