How Marijuana Works
Marijuana and the Brain

THC is a very potent chemical compared to other psychoactive drugs. An intravenous (IV) dose of only one milligram (mg) can produce serious mental and psychological effects. Once in your bloodstream, THC typically reaches the brain within seconds after it is inhaled and begins to go to work.

Marijuana users often describe the experience of smoking marijuana as initially relaxing and mellow, creating a feeling of haziness and light-headedness. The user's eyes may dilate, causing colors to appear more intense, and other senses may be enhanced. Later, feelings of a paranoia and panic may be felt by the user. The interaction of the THC with the brain is what causes these feelings. To understand how marijuana affects the brain, you need to know about the parts of the brain that are affected by THC. Here are the basics:

• Neurons are the cells that process information in the brain. Chemicals called neurotransmitters allow neurons to communicate with each other.
• Neurotransmitters fill the gap, or synapse, between two neurons and bind to protein receptors, which enable various functions and allow the brain and body to be turned on and off.
• Some neurons have thousands of receptors that are specific to particular neurotransmitters.
• Foreign chemicals, like THC, can mimic or block actions of neurotransmitters and interfere with normal functions.

In your brain, there are groups of cannabinoid receptors concentrated in several different places. These cannabinoid receptors have an effect on several mental and physical activities, including:

• Short-term memory
• Coordination
• Learning
• Problem solving

Cannabinoid receptors are activated by a neurotransmitter called anandamide. Anandamide belongs to a group of chemicals called cannabinoids. THC is also a cannabinoid chemical. THC mimics the actions of anandamide, meaning that THC binds with cannabinoid receptors and activates neurons, which causes adverse effects on the mind and body.

• High concentrations of cannabinoid receptors exist in the hippocampus, cerebellum and basal ganglia. The hippocampus is located within the temporal lobe and is important for short-term memory. When the THC binds with the cannabinoid receptors inside the hippocampus, it interferes with the recollection of recent events. THC also affects coordination, which is controlled by the cerebellum. The basal ganglia controls unconscious muscle movements, which is another reason why motor coordination is impaired when under the influence of marijuana.

Other Physiological Effects
In addition to the brain, the side effects of marijuana reach many other parts of the body. Marijuana is filled with hundreds of chemicals, and when it is burned, hundreds of additional compounds are produced. When marijuana is inhaled or ingested in some other form, several short-term effects occur. Some of the marijuana's side effects are:

• Problems with memory and learning
• Distorted perception
• Difficulty with thinking and problem solving
• Loss of coordination
• Increased heart rate
• Anxiety, paranoia and panic attacks

Ongoing studies now show a number of possible symptoms associated with the cessation of marijuana use. These symptoms most commonly include: irritability, nervousness, depression, anxiety and even anger. Other symptoms are restlessness, severe changes in appetite, violent outbursts, interrupted sleep or even insomnia. In addition to these possible physical effects, psychological dependence usually develops because a person's mind craves the high that it gets when using the drug.