A small study consisting of 18 participants has found that a possible drug-based treatment for severe bipolar depression may have some negative side effects.

The participants, all of whom suffered from manic depression, were given an average of seven different drugs. Of all the drugs, it was the anesthetic ketamine, which has been used legally in the U.S. since 1962, that provided the most benefit, according to the study that was published in the journal the Archives of General Psychiatry.

Those who were administered ketamine said their depressive symptoms improved 40 minutes after taking the drug, and that the effects lasted for at least three days.

However, some participants reported side effects associated with the drug, such as heightened anxiety and described feeling “woozy” and “loopy” at times. Others reported experiencing headaches and a temporary sense of disconnection from reality.

While bipolar disorder remains one of the more devastating condition for many, some feel the side effects associated with drug-related treatments aren’t a fair trade-off. Instead, many have embraced natural remedies such as omega-3 fatty acids and vitamin B12 to help with symptoms.