Ans is 'c' i.e. Caffeine is associated with the occurrence of the diseases [Ref: Park 20/e, p 69 (18/e, p 68, 17/e p64, 16/e,p62)[Cause and effect relationship is not established by case control study. It can be established by cohort study. A case control study cannot distinguish between causal factors and associated factors.A case control study can measure only the odd ratio ( an estimate of relative risk)A case control study does not establish a cause and effect relationship but it definately tells that caffeine is associated with the disease under study.