The present review investigates the relationship between polyunsaturated fatty acids (PUFAs) and mental health disorders, such as dementia, psychosis, schizophrenia, Alzheimer's disease, anorexia nervosa, and impairment problems in animals and human models. Data were collected from a variety of studies: randomized intervention trials, observational and interventional studies, case reports, and epidemiological studies. The evidence suggests that PUFAs are beneficial for mental health, brain function, and behavior. ALA, EPA, and DHA have very significant neuroprotective properties, particularly in inducing changes to the synaptic membrane and modulating brain cell signaling. In the case of neurodegenerative disorders, PUFAs incorporated into cellular membranes have been shown to protect against cell atrophy and death. The formal analyses of the included studies pointed to a decrease in ALA, EPA, and DHA levels in various populations (e.g., children, adolescents, adults, and seniors) presenting with different types of mental disorders. These results indicate that PUFA supplementation may be considered as an innovative therapeutic strategy to reduce the risk of neuronal degeneration.