 Because of similar and additive effects , divers should avoid sedating medications and drugs , such as marijuana and alcohol before any dive . A hangover , combined with the reduced physical capacity that goes with it , makes nitrogen narcosis more likely . Experts recommend total abstinence from alcohol for at least 12 hours before diving , and longer for other drugs . Abstinence time needed for marijuana is unknown , but owing to the much longer half @-@ life of the active agent of this drug in the body , it is likely to be longer than for alcohol . 
