Chunk #1 — Method — Sample

Source

Decline in genetic influence on the co-occurrence of alcohol, marijuana, and nicotine dependence symptoms from age 14 to 29.

Embedded

yes

Text

Additional analyses were conducted with a subsample of participants who had at least one symptom by their age-17 assessment for nicotine, alcohol, or marijuana dependence. This resulted in an “early-use” subsample of 580 males and 486 females.