We saw a 60-year-old male veterinarian with a history of autism spectrum disorder, major depressive disorder, and suicidality. He had been treated with more than 15 psychotropic medications, was admitted to inpatient care several times, and attempted suicide once. His current complaints included a decline in social functioning, repetitive behaviour, sensory hypersensitivity, anxiety, low mood, anhedonia, lack of energy, and chronic suicidality. His last medication consisted of risperidone and valproic acid. Despite intensive treatment, he remained impaired by his complaints and could not return to work. After self-medication with ketamine, he reported that his depressive and suicidal complaints disappeared and that his autism-related complaints diminished. This case - together with previous clinical research - suggests that ketamine is likely to be effective against depression and suicidality, that ketamine is potentially effective against autism-related symptoms, and that increasing awareness of the beneficial effects of ketamine can lead to unsupervised, and therefore risky, use of ketamine as a form of self-medication.