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. Author manuscript; available in PMC: 2016 Nov 1.
Published in final edited form as: Am J Psychiatry. 2015 Jun 5;172(11):1092–1100. doi: 10.1176/appi.ajp.2015.15010126

TABLE 5.

Co-Relative Control Analysis of Hazard Ratios for Nonaffective Psychosis and Chronic Obstructive Pulmonary Disease (COPD) Per Unit of Cigarette Exposure on a Three-Unit Scalea

Monozygotic Twins Full Sisters Half Sisters Cousins
Disorder and Comparison Estimate 95% CI Estimate 95% CI Estimate 95% CI Estimate 95% CI
Nonaffective psychosisb (N=3,790) (N=575,352) (N=153,938) (N=1,424,963)
  1–9 cigarettes/day versus none 1.30 1.07, 1.56 1.49 1.38, 1.60 1.59 1.52, 1.66 1.64 1.56, 1.74
  ≥10 cigarettes/day versus none 1.69 1.17, 2.44 2.21 1.92, 2.55 2.53 2.32, 2.75 2.70 2.42, 3.01
COPDc (N=3,802) (N=576,878) (N=154,442) (N=1,427,178)
  1–9 cigarettes/day versus none 1.71 1.45, 2.00 2.06 1.94, 2.18 2.26 1.7, 2.36 2.37 2.25, 2.51
  ≥10 cigarettes/day versus none 2.89 2.10, 3.99 4.23 3.76, 4.77 5.12 4.72, 5.55 5.63 5.05, 6.27
a

In the three-unit scale, one unit equals change from 0 to 1–9 cigarettes/day and from 1–9 to ≥10 cigarettes/day. Thus, the hazard ratio for change from 0 to ≥10 cigarettes/day equals the square of the depicted hazard ratio.

b

For the model, allowing for a different hazard ratio for each co-relative relationship, we get the following: −2logL=7,842.279 and Akaike information criterion (AIC)=7,850.279. For the model assuming linear dependence, we get the following: −2logL=7,842.743 and AIC=7,846.743. For monozygotic twins, p=0.0053; for all other groups, p<0.0001.

c

For the model, allowing for a different hazard ratio for each co-relative relationship, we get the following: −2logL=7,330.974 and AIC=7,336.974. For the model assuming the linear dependence, we get the following: −2logL=7,330.974 and AIC=7,334.974. For all groups, p<0.0001.