Although an increasing number of patients suffering from mental illnesses
self-medicate with cannabis, current knowledge about the efficacy and
safety of cannabis-based medicine in psychiatry is still extremely
limited. So far, no cannabis-based finished product has been approved for
the treatment of a mental illness. There is increasing evidence that
cannabinoids may improve symptoms in autism spectrum disorder (ASD), Tourette
syndrome (TS), anxiety disorders, and post-traumatic stress disorder (PTSD).
According to surveys, patients often use cannabinoids to improve mood, sleep,
and symptoms of attention deficit/hyperactivity disorder (ADHD). There is
evidence suggesting that tetrahydrocannabinol (THC) and THC-containing
cannabis extracts, such as nabiximols, can be used as substitutes in
patients with cannabis use disorder.Preliminary evidence also suggests an involvement of the endocannabinoid system
(ECS) in the pathophysiology of TS, ADHD, and PTSD. Since the ECS is the most
important neuromodulatory system in the brain, it possibly induces beneficial
effects of cannabinoids by alterations in other neurotransmitter systems.
Finally, the ECS is an important stress management system. Thus, cannabinoids
may improve symptoms in patients with mental illnesses by reducing stress.Practically, cannabis-based treatment in patients with psychiatric
disorders does not differ from other indications. The starting dose of
THC-containing products should be low (1–2.5 mg THC/day), and the dose should be
up-titrated slowly (by 1–2.5 mg every 3–5 days). The average daily dose is
10–20 mg THC. In contrast, cannabidiol (CBD) is mainly used in high
doses>400 mg/day.