A more recent 2018 article in the Journal of Clinical Psychopharmacology examined the effectiveness of CoQ10 supplementation in treating the depression cycle in bipolar disorder, which may be linked to oxidative stress.
A group of 69 patients with bipolar disorder, and who were undergoing a depressive episode, were randomized to receive either 200 mg per day of a CoQ10 supplement or a placebo for eight weeks. Any mood stabilizing medications remained the same for the duration of the study.
Patients in both groups showed a decrease in symptoms of depression over time, but the group taking CoQ10 showed better response at the end of eight weeks of treatment.
CoQ10 is well established as a powerful antioxidant. More recent research appears to show that this antioxidant benefit may also help improve symptoms of mood disorders.
Of course, you should always take a careful medical history, including any medications, before recommending CoQ10.