Through 30 years of scientific inquiry, NIDA research has demonstrated that drug addiction is essentially a brain disease, but of course drugs' destructive health effects extend beyond the intricate chemical pathways of the brain. Drug abuse and addiction have consequences that can be seen throughout the body--not just in brain scans, but in chest x-rays and blood tests.

For some drugs, these consequences are already well documented, yet the list of health warnings continues to grow. We know that nicotine addiction increases risks of heart and lung disease, cancers, and strokes. As dire as that list already is, NIDA-supported scientists are uncovering evidence of still more medical problems linked to smoking. For example, NIDA-supported researchers at Brookhaven National Laboratory in Upton, New York, recently demonstrated that smoking decreases levels of an important enzyme in the brain, heart, lungs, kidneys, and spleen. This enzyme, monoamine oxidase B (MAO-B), helps break down compounds that elevate blood pressure and plays a role in regulating dopamine levels in the brain. In smokers, MAO-B activity is reduced by one-third to one-half that seen in nonsmokers. This finding, which will be discussed in an upcoming issue of NIDA NOTES, may help clinicians identify--and treat--previously hidden health consequences of smoking.

Drug addiction is essentially a brain disease, but of course drugs' destructive health effects extend beyond the intricate chemical pathways of the brain.

Our picture of the medical consequences of other drugs is less comprehensive, but still grim. Abuse of heroin and other opiates is associated with consequences ranging from nausea and constipation to glomerulosclerosis, a life-threatening kidney disorder, and destruction of dental and orofacial structures. PCP (phencyclidine, or "angel dust") decreases heart rate and blood pressure, triggers violent aggression, and may trigger muscle contractions strong enough to break a bone. Methamphetamine ("meth," "speed," or "ice") causes cardiac damage, elevates heart rate and blood pressure, and can cause convulsions. Methamphetamine can also cause hyperthermia--elevated body temperature that results from disruption of the body's temperature-regulating mechanism. Methamphetamine increases wakefulness and physical activity, creating the potential for a combination of activity and overheating that leads to convulsions and dangerous, sometimes lethal elevation of body temperature.

NIDA-supported research has shown that cocaine restricts blood flow to the brain, increases heart rate, and elevates levels of blood components that promote clotting--effects that can lead to stroke or heart attack even in those not otherwise at risk for these dangerous cardiovascular events. Now, NIDA research suggests that cocaine also limits the body's ability to fight infection, putting cocaine abusers at greater risk for illnesses ranging from the common cold to hepatitis, sexually transmitted diseases, and HIV/AIDS (see "Cocaine May Compromise Immune System, Increase Risk of Infection").

The club drug ecstasy (methylenedioxymethamphetamine, or MDMA) can cause hyperthermia and is associated with kidney and liver damage. New NIDA-supported research suggests that MDMA also acts on serotonin receptor sites on heart valve cells, stimulating excessive cell growth. This overgrowth of heart valve cells in humans can lead to valvulopathy--a condition in which the valve becomes inefficient and blood leaks back into the heart (see "MDMA Use May Increase Risk for Cardiac Valve Disease"). NIDA-supported studies have shown that marijuana is associated with increased prevalence of respiratory problems, such as bronchitis, and possibly increased risk of cancers of the lung, head, and neck. We also are beginning to understand the scope of harm done by inhalants. Volatile solvents such as toluene damage the protective sheath around nerve fibers throughout the body. Chronic exposure to inhalants can produce significant damage to the heart, lungs, liver, and kidneys.

Some of the destructive medical consequences of drug abuse and addiction are temporary--the conditions improve after patients receive treatment and are able to stop their drug use. Other consequences may be more persistent, diminishing the quality of patients' health long after drug use has stopped.

The extent of drugs' impact on general health was recently highlighted in a study by NIDA-supported investigators at the University of California, San Francisco, and the Kaiser Permanente health maintenance organization (HMO). The researchers compared the general health of 747 patients enrolled in the HMO's drug dependence treatment programs with that of more than 3,600 health plan members without any history of substance abuse. They found that substance-abusing patients also suffer from a wide variety of other health problems, including injuries associated with overdose; pain-related conditions such as headache, lower back pain, and arthritis; hypertension; pneumonia; heart disease resulting from decreased blood supply to cardiac muscle; pulmonary disorders; and asthma.

Some of the destructive medical consequences of drug abuse and addiction are temporary--the conditions improve after patients receive treatment and are able to stop their drug use. Other consequences may be more persistent, diminishing the quality of patients' health long after drug use has stopped. Whether short-lived or chronic, the growing list of recognized health consequences of abuse and addiction underscores the fact that drug abuse is not just a brain disease that exists in medical isolation--it manifests itself throughout the body with a broad array of medical consequences. Thus, it is important for the entire medical community--general practitioners, pediatricians, and dentists as well as addiction specialists--to recognize a full range of diagnostic signs of abuse and addiction. Drug abuse treatment can be integrated into the spectrum of care provided by the general medical community. For example, buprenorphine and naloxone now can be used to treat opiate addiction in a physician's office rather than in a specialized clinic setting.

Our research adds important detail to the terrible picture of addiction's pervasive harm--which cannot and should not be considered in isolation from general health issues--and it may also reveal new possibilities for treatments that heal not just the brain, but the whole body.

NIDA's interest in the medical consequences of addiction extends beyond the brain and includes all age groups and every abused drug. Our research adds important detail to the terrible picture of addiction's pervasive harm--which cannot and should not be considered in isolation from general health issues--and it may also reveal new possibilities for treatments that heal not just the brain, but the whole body.

Volume 18, Number 6 (February 2004)