http://www.datia.org/advocacy/IBH_workplacetesting.pdf (Section IV)
"In 2002 the estimated national cost of lost worker productivity including absenteeism and poor job performance due to illicit drug use was $129 billion. This cost directly impacts employers, fellow employees, and families and indirectly, the nation’s economy. Employees who use drugs are more likely to ask for early dismissal or time off, to be absent, to be late for work, to be involved in workplace accidents, and to file workers’ compensation claims. Additionally, past month illicit drug users are more likely than their non-using peers to report having worked for three or more employers in the past year. Results from a blind longitudinal study of job applicants show that individuals who test positive on pre-employment tests are 77 percent more likely to be terminated within the first three years of employment and be absent from work 6 percent more frequently.
Among adults age 18 and older, 9.1 percent of full time employees used an illicit drug in the past month in 2013, compared to 13.7 percent part-time employees and 18.2 percent of those who are unemployed. Although drug use is more prevalent among those not employed, 68.9 percent of all illicit drug users aged 18 and older (15.4 million) were employed full or part-time. For decades marijuana has been and remains the most widely used illicit drug among those who are employed. A national study of worker substance use showed that for years 2002-2004, 6.4 percent (7.3 million) of full-time workers aged 18 to 64 used marijuana in the past month.
** This represented the large majority (77.6 percent) of those who used an illicit drug during this time.
The serious threats to health and safety created by the use of marijuana were recently reviewed in two leading medical journals. Marijuana is a drug of abuse that can produce addiction and symptoms of withdrawal. About 9 percent of all marijuana users develop addiction to the drug. This figure increases dramatically to 17 percent if marijuana use is initiated during adolescence and increases to between 25-50 percent among daily marijuana users. The early and heavy use of marijuana increases the risk of addiction to marijuana and it also increases risk of use and addiction to other drugs. Over 61 percent of Americans age 12 and older with a substance use disorder for drugs other than alcohol are dependent on or abuse marijuana, making it by far the most prevalent illicit drug of abuse in the country. More Americans obtain treatment for marijuana than for any other illegal drug.
In addition to the link between early and heavy marijuana use and addiction, there is a strong association between marijuana use and diminished lifetime achievement; motor vehicle crashes; and symptoms of chronic bronchitis. There is also a relationship between marijuana use and abnormal brain development, progression to use of other drugs, schizophrenia, depression and anxiety.
Short-term effects of marijuana use include impaired short-term memory, impaired motor coordination, altered judgment and, in high doses, paranoia and psychosis. Among the conclusions reached by Colorado’s Retail Marijuana Public Health Advisory Committee charged with monitoring health effects of marijuana and released by the Colorado Department of Public Health and Environment, “We found substantial evidence for associations between marijuana use and memory impairments lasting at least seven days after last use, as well as the potential for acute psychotic symptoms immediately after use” Given the short- and long-term impacts of marijuana use, the drug poses a serious threat to workplace safety and productivity. The legal status of marijuana does not remove this threat."