Objective An 18-year-old man with Arnold–Chiari malformation (ACM) type I developed sudden panic attacks. He also manifested sleep disorder, cannabis abuse, and psychosis-risk syndrome (PRS). Although with average–superior intelligence, he had executive dysfunction. This prompted us to explore the relation between ACM, cannabis abuse, PRS and panic disorder. Method We report the case and briefly review the literature focusing on ACM and psychiatric disorders. Results Behavior therapy led to gradual abstinence from cannabis with disappearance of anxiety symptoms. The patient is currently well and maintained on omega-3 polyunsaturated fatty acids. Conclusions Locus coeruleus compression and cannabis abuse may have triggered the symptoms, and the latter might also be PRS-related. PRS and anxiety symptoms should be explored in ACM patients to allow better prevention of psychosis and anxiety disorders.