The story usually runs one direction: your environment shapes your behavior. Spend time with heavy drinkers, and your drinking drifts up. That part is probably true. The half I keep thinking about in a new systematic review is the reverse. Your drinking habits also shape who you end up spending time with.

The review, published in Frontiers in Public Health, pulled together 27 studies that applied whole network analysis (WNA) to four behaviors: smoking, alcohol consumption, physical activity, and diet. The question was how these behaviors spread and take root inside a social system.

What they did

Researchers screened six academic databases for empirical studies using WNA, following PRISMA 2020 guidelines. 27 studies made the cut.

The filter that matters here is sociocentric data. Most behavior research is egocentric - you ask someone about their personal network ("who do you spend time with?"). WNA maps every relationship inside a defined population instead. Everyone, not a sample of everyone's memory.

What they found

Four mechanisms showed up across all four behaviors:

  • Peer influence. Connected people adopt each other's behaviors over time.
  • Homophily. People with similar behaviors cluster together. Drinkers end up in circles with drinkers - which means the "heavy drinking crowd" is partly something you assembled, not something you walked into.
  • Network cohesion. Tight groups reinforce behavior harder than loose ones.
  • Centrality. A handful of structurally central people carry disproportionate weight in which norms spread.

WNA also turned out to be good at spotting behavior clusters - subgroups where a behavior has concentrated - and at capturing co-evolutionary dynamics, where network structure and behavior shift together over time.

The clearest findings came from longitudinal studies using stochastic actor-oriented models (SAOMs). These separate two effects that usually get conflated: selection (you chose friends who drink like you) and influence (your friends changed your drinking). Most studies found both running at once.

What it means

Most people treat their social environment as something that happened to them. WNA points the other way too. Your habits helped build that environment.

Centrality is the most actionable piece. In any group, a small number of people sit at structural hubs - many connections, high overlap across subgroups. Their behavior sets the norm quietly. If someone central shifts how they drink, the cluster tends to follow. Not a prescription. Just how diffusion works.

And the two move together. The social system you're in today is partly a product of the habits you've had over the last few years.

Caveats

27 studies is a thin base for a review like this. The search was English-only, which likely underrepresents non-Western research. The included studies vary widely in design, population, and method - some ran full longitudinal SAOM approaches, others didn't. Clean generalization gets hard fast.

One structural limit the authors flag: WNA needs complete data on an entire network. Logistically demanding, and rarely feasible in ordinary public health settings.

Source: Frontiers in Public Health, doi:10.3389/fpubh.2026.1834356