Intended for healthcare professionals

Rapid response to:

Head To Head Head to Head

Should the supply of cannabis be legalised now?

BMJ 2019; 366 doi: (Published 03 July 2019) Cite this as: BMJ 2019;366:l4473

Rapid Response:

Cannabis and copper and zinc upsets increase the risk of psychosis? Re: Should the supply of cannabis be legalised now?

Stavros Saripandis writes that cannabis use shrinks the brain areas related to reward and learning .

I posted this BMJ rapid response in 2004 which contains information that may be useful.

"A clue why the risk of cannabis-psychosis is four times more likely in young people with predisposing factors, may be found in the results of animal studies of the interactions with copper and zinc and cannabis.1 Copper potentiated the barbiturate hypnosis-potentiating activity of cannabis. Single doses of copper partially inhibited tolerance to barbiturate hypnosis-potentiation activity and markedly delayed the development of tolerance to hypothermic activity of cannabis for one to two weeks.2

Many patients prone to mental instability have difficulty in maintaining a normal copper/zinc balance. Zinc deficiency is extremely common and is increased with smoking tobacco and drinking alcohol. Men have lower zinc levels than women and need extra zinc during growth. Menstruating females have higher copper levels than males. If women also use progesterone contraceptives or menopausal hormones, high monoamine oxidase levels and even higher than usual copper levels increase the risk of mental illnesses and suicide attempts.3,4 Infections also increase copper levels. Copper stores may become depleted and copper deficiency impairs Cu/Zn superoxide dismutase activities.

These important homeostatic imbalances increase adverse reactions to foods and chemicals. Zinc and copper deficiency or high copper levels can also block essential fatty acid pathways, causing both omega-6 and omega-3 deficiencies, and also vitamin B group deficiencies, which further increase the risk of psychosis. Monitored nutritional supplementation with 1mg doses of copper in the morning and 30 mg doses of zinc in the evening for two or three weeks can give a rapid improvement in many conditions. In particular, the resolution of mental or neurological illnesses can be very dramatic.

1 Henquet C, Krabbendam L, Spauwen J, et al. Prospective cohort study of cannabis use, predisposition for psychosis, and psychotic symptoms in young people BMJ 2004; 0: bmj.38267.664086.63v1
2 Singh PP, Das PK. Studies on the interactions of copper and cannabis. Psychopharmacology (Berl). 1978 ;56 : 309-16.
3 Grant ECG. The Pill, Hormone Replacement Therapy, Vascular and Mood Over-reactivity, and Mineral Imbalance. J Nutr Environ Med 1998; 8:105- 116.
4 Price EH. Increased Risk of Mental Illness and Suicide in Oral Contraceptive and Hormone Replacement Therapy Studies 1998; 8: 121-127."

Competing interests: No competing interests

06 July 2019
Ellen CG Grant
Physician and medical gynaecologist
Kingston-upon-Thames, Surrey, UK