In this section we formulate a mathematical model of alcohol abuse. The
adult human population is divided into four different classes, namely, moderate
and occasional drinkers with frequency S(t), heavy drinkers with frequency
D(t), drinkers in treatment with frequency T(t), temporarily recovered class
with frequency R(t) at time t.
We diagrammatically represent the flow of individuals from one class to the
other in figure below.
The model can be presented by the following set of ordinary differential equations: