The genes linked to potential development of schizophrenia may also be a factor in a person's use of marijuana, according to a research team at the Institute of Psychiatry at King's College London.
The common psychiatric disorder impacts one in 100 and those who use pot are twice as likely to develop the disorder, say researchers.
"We know that cannabis increases the risk of schizophrenia. Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as well -- that a pre-disposition to schizophrenia also increases your likelihood of cannabis use," said Robert Power, who led the study at the Institute of Psychiatry at King's College London.
The study involved just over 2,000 participants, of which half, 1,011, use marijuana. Each participant's genetic risk profile was measured during the research. The results, says Power, "highlights the complex interactions between genes and environments" when it comes to marijuana as a risk factor for schizophrenia.
"Certain environmental risks, such as cannabis use, may be more likely given an individual's innate behavior and personality, itself influenced by their genetic make-up," he said, adding "I wouldn't say that there's no risk of cannabis causing schizophrenia, but that it's probably more complex a relationship that we are currently thinking."
The latest research arrives shortly after another study that linked marijuana use by middle-aged adults to potential increased risks for develop cardiovascular-related complications.
According to the Journal of the American Heart Association, almost 2 percent of health problems caused by marijuana use were related to cardiovascular condition and a fourth of these led to death. The study studied 1,979 complications linked to marijuana use and 35 of these were heart-related, 10 were diseases related to limb arteries, 20 suffered heart attacks and 22 were heart-related. Nine patients among the 35 cases or 25.6 percent, died from cardiovascular complications. There is evidence that use of marijuana may increase blood clotting and significant effects in the tiny vessels that bring blood to the brain and heart that even after the blockage is cleared, the flow remains slow.
"One is left to wonder whether we need to consider 'pot heart' in addition to 'pot head,' " NYU Langone Medical Center associate professor of medicine in cardiology Dr. Sripal Bangalore told CBS News. "Nevertheless, the growing body of evidence suggests that similar to statutory warning on smoking, similar warning should perhaps be considered for recreational marijuana use."
Previous research suggests that marijuana users usually develop substance abuse or dependence on alcohol and other drugs. Bangalore also notes that it is more difficult to detect the effects of marijuana in those who also drink alcohol and smoke tobacco.
"In prior research, we identified several remarkable cases of cardiovascular complications as the reasons for hospital admission of young marijuana users," said author and medical faculty member at Centre Hospitalier Universitaire de Toulouse Emilie Jouanjus, Pharm.D., Ph.D. "This unexpected finding deserved to be further analyzed, especially given that the medicinal use of marijuana has become more prevalent and some governments are legalizing its use."
Recent studies also connect marijuana use in people suffering for ischemic ulcers, increased angina and gangrene which is a blood flow blockage to extremities and ministrokes or transient ischemic attacks. Other health problems associated with marijuana use are obesity, high blood pressure, sedentary behavior and high cholesterol. People with existing cardiovascular issues are more prone to the dangerous effects of marijuana.
