Hangovers are causing 11.5 million "sick days" a year at a cost of $3 billion to the Australian economy, new research suggests.

There are also fears that people who are mixing alcohol with amphetamines on the weekends are experiencing "Weepy Wednesdays" because of the delayed effects of their drug use, making them irritable and unreliable workers.

A new study has found that the more alcohol and drugs an employee consumes, the more time they are likely to take off work. Credit:Arsineh Houspian

A Flinders University study has found that the more alcohol and/or drugs an employee consumes, the more time they are likely to take off work.

After tallying the total cost of this lost productivity at $3 billion a year - up from $1.2 billion in alcohol-related absenteeism alone in 2001 - the researchers said employers should be looking at ways to promote a healthier culture in their workplace especially around alcohol, which is by far the biggest problem.