RT Journal
A1 Kendler KS, Ohlsson H, Sundquist K, Sundquist J
T1 Within-family environmental transmission of drug abuse: A swedish national study
JF JAMA Psychiatry
JO JAMA Psychiatry
YR 2013
FD February 1
VO 70
IS 2
SP 235
OP 242
DO 10.1001/jamapsychiatry.2013.276
UL http://dx.doi.org/10.1001/jamapsychiatry.2013.276
AB Context 
                  Drug abuse (DA) strongly runs in families. Does this result solely from genetic factors or does the family environment contribute?Objective 
                  To determine the familial environmental contribution to the risk for DA.Design 
                  Follow-up in 9 public databases (1961-2009) in siblings and spouses.Setting 
                  Sweden.Participants 
                  A total of 137 199 sibling pairs and 7561 spousal pairs containing a proband with DA and matched control probands.Main Outcome Measures 
                  Drug abuse recorded in medical, legal, or pharmacy registry records.Results 
                  In the best-fit model, which contained significant linear, quadratic, and cubic effects, among full sibling pairs containing a proband with DA, the relative risk for DA in the sibling declined from more than 6.0 for siblings born within 2 years of each other to less than 4.5 when born 10 years apart. Controlling for age differences in full sibling pairs, the hazard rate for DA in a sibling when the affected proband was older vs younger was 1.42 (95% CI, 1.31-1.54). In the best-fit model, which contained significant linear, quadratic, and cubic effects, among spousal pairs containing a proband with DA, the relative risk for DA in the spouse declined from more than 25.0 within 1 year of proband DA registration to 6.0 after 5 years.Conclusions 
                  Controlling for genetic effects by examining only full siblings, sibling resemblance for the risk for DA was significantly greater in pairs closer vs more distant in age. Older siblings more strongly transmitted the risk for DA to their younger siblings than vice versa. After one spouse is registered for DA, the other spouse has a large short-lived increase in DA risk. These results support strong familial environmental influences on DA at various life stages. A complete understanding of the familial transmission of DA will require knowledge of how genetic and familial environmental risk factors act and interact over development.