Effect of marihuana on hearing.

Marihuana has been said to improve hearing. Two earlier studies have supported this contention. In this investigation, marihuana or placebo cigarettes were randomly smoked by 30 subjects, 15 in each group. Before and after smoking, batteries of standard audiological tests were carried out; pure tone threshold (air and bone conduction), speech reception threshold, speech discrimination at most comfortable level, and relative acoustic impedance measurements including middle ear pressure, stapedial reflexes, compliance, tympanic mobility, and Eustachian tube function. A comparison of pre and post smoking auditory test scores did not demonstrate any significant change in auditory function in the marihuana or placebo group. However, as all subjects had normal hearing and maximum speech discrimination scores pre-smoking, it can only be concluded that smoking marihuana did not worsen the hearing--the experiments were not designed to see whether it would improve hearing.