The United States is in the midst of an unprecedented drug-overdose crisis. Roughly 120 people die of a drug overdose everyday. Among white Americans ages 25 to 34 the overdose death rate in 2014 was five times its 1999 level, according to data from the Centers for Disease Control and Prevention.

“The number of people now dying from drug overdose is comparable to the number dying annually from AIDS during the peak of the AIDS epidemic in the mid-90s,” Talking Points Memo editor Josh Marshall wrote on Jan. 26. The comparison puts the current drug-overdose epidemic in perspective, but the more important parallel here is that both crises were caused, at least in part, by inequality and the deprivation and despair that inequality creates.

Inequality became understood as a public health problem with the introduction in 1995 of the Fundamental Causes approach, which maintains that access to economic and social resources have a huge influence on health. Moreover, while the immediate causes of health disparities may vary, social inequalities such as poverty, discrimination and prejudice will always have a negative effect on health through one mechanism or another.

The HIV/AIDS and drug overdose epidemics are perfect examples of how socioeconomic inequalities affect public health. In the case of HIV/AIDS, HIV stigma can push people to do things that might transmit the disease, like having unprotected sex. And those facing such stigma are more likely to have poor access to health care. In other words, stigmatizing HIV-positive people can lead to unnecessary AIDS-related deaths.

Income inequality is one of the main drivers of the increase in drug-overdose deaths. Similar increases in alcohol-related deaths and suicide have also been ascribed to the rising income gap. In fact, the increase in drug overdose deaths appears to mirror an increase in economic inequality in the United States since mid-1980s.