This work has a few notable limitations. First, our outcome measure is not a clinical tool, so we cannot make any specific conclusions about the spread of alcohol related disorders per se in our sample. Second, it is not possible to estimate the relative negative health impact of increasing alcohol use, since alcohol use has been reported to have both positive and negative health effects. For example, moderate alcohol use is consistently associated with a lower risk (relative to abstention) for myocardial infarction in prospective cohort studies (43). This beneficial effect of moderate alcohol intake has been found to hold even for men with relatively healthy lifestyles (44,45). In addition to these cardiovascular effects, some evidence also suggests that mild to moderate alcohol intake may be related to better cognitive functioning in older adults (46). Therefore, network effects that both increase and decrease alcohol consumption could have health benefits. Third, this sample is ethnically (but not socioeconomically) homogenous. Finally, all network ties are observed in the dataset. This leaves open the potential that our estimates may be biased.
