New research suggests that heavy drinkers and users of illegal drugs downplay their relative levels of consumption, when comparing themselves to others.

Researchers from the London School of Economics and Political Science (LSE) and South London and Maudsley NHS Foundation Trust found that 68 percent of respondents to the Global Drugs Survey (GDS) -- the world's biggest drug survey -- were drinking at hazardous or harmful levels, yet the vast majority (83 percent) felt they were drinking at low or average levels.

Researchers found that this same pattern occurred across a range of illegal drugs. Although frequent and/or heavier users were more likely to judge their use to be above average than moderate users they still tended to downplay their levels of use. For example, the survey showed that using cannabis every day or most days was fairly unusual yet a third or more of respondents who used cannabis this frequently considered their use to be average (33 percent) or less than average (42 percent).

For ecstasy and cocaine, more than half of even the heaviest users thought they were using at no more than average levels.

"Given that drug use carries certain risks, whether this be to health, of getting caught or of damage to reputation, we shouldn't be surprised that some people downplay their levels of use as a way of managing their anxieties about what they're doing," Dr. Michael Shiner, an associate professor in LSE's Department of Social Policy and expert advisor to the Global Drugs Survey, said in a statement.

Regardless of respondents actual drinking habits, those who thought they were drinking at a high rate compared to others were almost twice as likely to want to cut down as those who thought they were drinking at average levels. Similar effects were evident in relation to cannabis, ecstasy and cocaine.

The findings are detailed in the journal Social Science & Medicine.