Marijuana: Health Effects and Risks

Marijuana (cannabis) has a significant impact on the brain and body. Claims that marijuana is not addictive or does not have long-term health effects are not supported by current scientific evidence. Research indicates that marijuana use—particularly chronic, heavy, or early use—can have adverse effects on physical health, mental health, and social functioning.

Like all drugs and medications, marijuana has a side-effect profile, meaning it can produce unintended negative effects in addition to any desired effects. Whether marijuana is used recreationally or for medical purposes, its active compounds affect multiple organ systems. With frequent or prolonged use, these effects may contribute to impairment or illness.

The following information summarizes health effects associated with marijuana use that have been documented in research studies. For more detailed clinical discussion and references, please see the Healthcare Professionals section.

Effects on Brain Function

Short-Term Effects

Marijuana intoxication is associated with impairments in several brain functions, including:

• memory

• perception of time

• sensory processing

• attention and concentration

• problem-solving

• verbal fluency

• reaction time

• psychomotor coordination

These short-term effects typically last one to four hours, depending on the potency of the marijuana, route of administration, and individual tolerance. During this period, activities requiring alertness and coordination—such as driving—may be significantly impaired.

Long-Term Effects

Heavy or long-term marijuana use has been associated with subtle but persistent impairments in memory, attention, learning, and information processing.

Children and adolescents appear to be more vulnerable to these effects because brain development continues into early adulthood. Risk may be increased when marijuana is used in combination with alcohol.

Psychosocial Health

Mental Health

Research indicates that marijuana use may be associated with:

• development of cannabis use disorder (addiction)

• psychotic symptoms, including difficulty distinguishing what is real from what is not

• increased risk of schizophrenia, particularly in individuals with a personal or family history of psychotic disorders

• anxiety, panic symptoms, and depressive disorders

Risk appears to be higher with early onset of use, frequent use, and high-potency products.

Social Functioning

Marijuana use has been associated with challenges in educational and occupational functioning.

Among adolescents—especially those with pre-existing academic difficulties—use may contribute to poor school performance or school failure, which can affect long-term opportunities.

Among adults, frequent marijuana use has been associated with lower occupational attainment and higher rates of unemployment.

Physical Health

Respiratory and Cardiovascular Effects

Marijuana smoke contains many of the same irritants and toxins found in tobacco smoke. Smoking marijuana may:

• irritate and inflame the airways

• contribute to chronic bronchitis

• cause cellular changes in the respiratory tract that are associated with increased cancer risk

Marijuana can also increase heart rate and blood pressure, which may elevate the risk of cardiac events in individuals with underlying heart disease.

Reproductive and Developmental Effects

Compounds found in marijuana can cross the placenta during pregnancy and are present in breast milk.

Marijuana use during pregnancy and early development has been associated with:

• low birth weight

• developmental delays

• behavioral difficulties later in life

Marijuana also affects aspects of reproductive physiology in both men and women, although the long-term consequences of these effects are still being studied.

Summary

Marijuana use carries potential health risks, particularly when use is frequent, heavy, begins early in life, or occurs in vulnerable individuals. Ongoing research continues to refine understanding of these risks.

For additional clinical detail and references, please refer to the Public Policy section.

If you’re looking for broader information about addiction and recovery, explore Addiction Education & Support.