About one in three Massachusetts residents who use marijuana say they have driven while under the influence of the drug.
That's among the findings of a statewide study of marijuana use released Friday by the Department of Public Health.
In all, about 21 percent of those surveyed by the agency said they had used marijuana within the last 30 days, with the highest proportion of users between ages 18 and 25.
More than 34 percent said they had driven at least once after getting high, while 11 percent of all adults reported having been in a car driven by a person who had used marijuana in the last 30 days.
The study found that smoking is the most common method of marijuana use, although 40 percent of users report multiple methods of use.
A survey of patients who use marijuana products for medical use suggests the average person uses marijuana 24 days a month.
The study also showed that marijuana will increase state revenue by about $215.8 million in the first two years of retails sales. This will come mostly from sales and excise taxes collected on retail purchases.
Lawmakers called for the study as it made revisions last year to the state's voter-approved recreational marijuana law.