Some general effects of smoking marijuana:
· The more marijuana is used, the shorter its effects last.
· Tolerance to the psychoactive effects develops with continued use.
· Psychological and mild physical dependence gradually occurs with regular use.

The cannabinoid effect may be additive to nitrogen narcosis.

Carbon monoxide retention leads to high partial pressures of CO at depth - severely reducing oxygenation of red blood cells and tending toward hypoxia on ascent.

Withdrawal symptoms include:
Restlessness, insomnia, nausea, irritability, loss of appetite, sweating.
· Risk of adverse reactions is greater for persons who have had schizophrenia or other psychotic disorder, depression, dysthymia, and bipolar disorder (manic-depression).
· Tar content of marijuana is significantly greater than cigarettes, with more carcinogens.

Risks to diver of cascading events leading to near-drowning or arterial gas embolism.

Potentially harmful effects to divers include:
· Accidents and deaths caused by distortions in perception of time, body image, and distance.
· Impairment of recent memory, confusion, decreased concentration.
· Decreased muscle strength and balance.
· Decreased blood flow in brain.
· Impaired ability to perform complex motor tasks.
· Poor memory.
· Amotivational syndrome.
· Depression, especially in new users.
· 50% of users will have a "bad trip" - severe panic reaction with fear of dying or losing one's mind.
· Fast heart rate and lower exercise tolerance.
· Dry mouth and throat.

High doses may cause:
· Hallucinations
· Depersonalization
· Paranoia
· Agitation
· Extreme panic

Risks to divers -- cascading events leading to drowning and death. Possible injury to buddy and others in dive party.

Chronic use may cause:
· Bronchitis, Sinusitis, Pharyngitis, Chronic cough, Emphysema, Lung cancer. Pulmonary blebs (with barotrauma)
   
 Risk to divers --pulmonary barotrauma, overexpansion injury, arterial gas embolism.

· Poor immune system functioning;
    
Risk to divers -- severe marine infections.

Poor motivation, depressed mental functioning.
  
  Risk to divers -- errors of omission, commission with cascading events leading to drowning.