A family tendency relates to the presence of a disease or condition in the parents or grandparents of an individual. This statistically increases a person's likelihood of being affected by the same condition.
Family tendency is not synonymous with a genetic link. It indicates there is a statistical increase of prevalence among the direct descendants of disease sufferers. In the case of heart disease, family medical history is an indicator of risk. This is combined with other factors, including weight, exercise habits, diet, cholesterol levels, alcohol and tobacco use.
Some mental health conditions also show a family tendency. The likelihood that a parent, sibling or child of a suicide victim also commits suicide is higher than the risk found in the general population. This fact correlates to the family tendency for depression. This is not due to a gene, but other inherited biological traits that may indicate susceptibility to depression. These include a thinning of the right and left cortex of the brain.
A family tendency is not a guarantee that a member of the family is going to be affected by the same medical conditions that plagued their ancestors. It is a risk indicator that interacts with other environmental and physical factors.