Two systems are said to be in chemical equilibrium with each other when their chemical potentials are same. 3) Thermal equilibrium: When the system is in mechanical and chemical equilibrium and there is no spontaneous change in any of its properties, the system is said to be in thermal equilibrium.
While scientists have known for some time that genetics play a role in alcoholism and other addictions, they also understand the tendency to be dependent on alcohol is more complicated than the simple presence or absence of any one gene.
No one knows exactly what causes it, but depression does appear to have a genetic component. While your genetic makeup can certainly factor into whether or not you end up with depression, this only means that you are potentially more susceptible to developing depression, not that you necessarily will.