Prevalence of Marijuana Use in Lifetime, Past Year, and Past Month among Persons in the US Aged 12 or Older, by Demographic Characteristics: Number in Thousands

"26.4% of Irish adults aged 15 years or older report using an illegal drug in their lifetime, 7.5% in the past 12 months and 4.0% in the past month.
"• Lifetime usage of cannabis (24.0%) is considerably higher than any other form of drug. The second most commonly used drug is ecstasy (7.8%) with lifetime usage of cocaine (including crack) and cocaine powder at 6.6% and 6.4% respectively.

Prevalence of Alcohol Use Among Young People in Australia: "Alcohol use becomes more common with increasing age with 76% of 17-year-olds having consumed alcohol in the year preceding the survey, compared to 19% of 12-year-olds.
"Only 32% of all students reported never consuming alcohol.

Prevalence of Non-Medical Tranquilizer Use Among Young People in Australia: "Around 17% of students had used tranquilisers other than for medical reasons at some point in their life. The proportions of students ever using tranquilisers increased from 13% of 12-year-olds to around 19% of 15- to 17-year-olds.
"Use in the past month was low in all ages and reached only five per cent among students aged 14 and over.
"Across all ages, around two per cent of secondary school students had used tranquilisers in the week before the survey.

Prevalence of Analgesic Use Among Youth in Australia: "Regularity of use: Of students who had used analgesics in the past year, 54% of females and 43% of males had used analgesics 10 or more times in the previous year. Sixteen per cent of males and 10% of females reported use of analgesics only once or twice in the past year.
"Of the male students who had used analgesics in the past week, 71% had used them only once or twice, while 20% had used them 3-5 times. Of the female students who had used analgesics in the past week, 68% had used them once or twice and 22% had used them 3-5 times."

Estimated Prevalence of Illicit Drug Use Among Youth in Australia: "Analgesics: Analgesics were the most commonly used substance (licit or illicit) with 95% of students aged 12 to 17 years having used an analgesic at some time in their lives. Females were more likely than males to use analgesics in all recency periods with for example 48% of females using analgesics in the week prior to the survey compared to 34% of males. The main reason for analgesic use was to help ease the pain associated with a headache/migraine (52%). For the majority of students (90%) parents were the main source of analgesics.

Estimated Prevalence of Current Illicit Drug Use In The US By People 12 Or Older, by Race and Ethnicity: "In 2015, an estimated 27.1 million Americans aged 12 or older were current (past month) illicit drug users, meaning that they had used an illicit drug during the month prior to the survey interview (Figure 1). The most commonly used illicit drug in the past month was marijuana, which was used by 22.2 million people aged 12 or older. An estimated 6.4 million people reported misusing psychotherapeutic drugs in the past month, including 3.8 million people who were misusers of prescription pain relievers. Thus, the number of current misusers of pain relievers was second to marijuana among specific illicit drugs. Smaller numbers of people in 2015 were current users of the other illicit drugs shown in Figure 1.

Teen Drug Use and Risk of Future Addiction Disorder: "Teen users are at significantly higher risk of developing an addictive disorder compared to adults, and the earlier they began using, the higher their risk. Nine out of 10 people who meet the clinical criteria for substance use disorders involving nicotine, alcohol or other drugs began smoking, drinking or using other drugs before they turned 18. People who begin using any addictive substance before age 15 are six and a half times as likely to develop a substance use disorder as those who delay use until age 21 or older (28.1 percent vs. 4.3 percent)."

"Early Drug Exposure and Later Drug Use: "The teen brain is a work in progress, making it more vulnerable than the mature brain to the physical effects of drugs. The potential for developing substance abuse and dependence is substantially greater when an individual’s first exposure to alcohol, nicotine and illicit drugs occurs during adolescence than in adulthood."

Estimated Prevalence of Current Tobacco Use Among Pregnant Women in the US