Long-term harmful effects of marijuana include risk for heart attacks and strokes in addition to impaired learning and memory.

The active chemical in marijuana, called delta-9-tetrahyrdocannabinol (THC), is believed to exert these effects by binding to cannabinoid (CB) receptors located on several cell types in various organs.

Scientists have found CB receptors in many organs including the brain, heart, liver, kidney, and spleen. In this study, researchers investigated if persistent heavy marijuana use might be associated with changes in different blood proteins in order to check if the abnormalities in the identified proteins might be related to other side-effects of marijuana.

The study was conducted with 18 long term heavy marijuana users and 24 non-drug using volunteers. People with major medical and psychiatric illnesses, hypertension, head injury, HIV positive, alcohol dependency and other drug usage, were excluded from the study. Blood proteins were measured in both control volunteers and marijuana users using a new method (protein chip) that has the potential to identify several new target proteins.

That approach showed that apolipoprotein C-III (apoC-III) showed significant increases in marijuana abusers. ApoC-III belongs to a large family of proteins that interact with lipids and helps lipids to move into and out of cells. ApoC-III is involved in transport of triglycerides and delays the breakdown of triglycerides. Increases in apoC-III levels in the blood occur in parallel with increases in triglyceride levels.

Even though it is unclear how heavy marijuana use might cause increases in apoC-III levels, this protein might be one of the reasons why some marijuana users have increased risks of heart attack and strokes.

Citation: Heavy Marijuana Users show Increased Serum Apolipoprotein C-III levels: Evidence from proteomic analyses
S Jayanthi, S Buie, S Moore, RI Herning, W Better, NM Wilson, C Contoreggi, JL Cadet, Molecular Psychiatry advance online publication 13 MAY 2008 – 05:00 PM EST