A study by the Max Planck Institute found that zebrafish with a mutation in the glucocorticoid receptor—a key component of the stress response—displayed behaviors akin to depression. These fish exhibited elevated stress hormone levels and reduced responsiveness to new environments. Notably, their behavior normalized when exposed to the antidepressant fluoxetine (Prozac), indicating a direct link between stress and depression-like symptoms.

Social Isolation in Zebrafish: Studies have demonstrated that zebrafish deprived of social interaction exhibit increased anxiety and altered brain activity. These changes are linked to serotonin modulation, and the fish's behavior could be normalized by reducing serotonin levels, highlighting the role of neurochemicals in mood regulation.

Social Stress in Nile Tilapia: Research on Nile tilapia exposed to social stressors showed elevated cortisol levels and behavioral changes, such as altered body coloration, indicative of stress. These responses are similar to those observed in mammals under chronic stress, suggesting that fish can experience depression-like states.

Apparently yes.