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When does a normal human instinct cross over into a harmful addiction? Steve Sussman, PhD, a professor of preventive medicine, psychology, and social work at USC’s Institute for Health Promotion & Disease Prevention Research, has a simple guideline:

“If it doesn’t carry a negative consequence, then it’s not negatively consequential; it’s a passion.”

Plenty of people enjoy activities in moderation. But when it adversely affects your life, your work, or your family — when you have a preoccupation with it and you’re miserable without it. When you lose control over when you are engaged in the activity, over and over. Then there’s a problem.

Sussman and a small army of other researchers explain it all in a new textbook: The Cambridge Handbook of Substance and Behavioral Addictions, published recently by Cambridge University Press, and which Sussman edited.

The tome functions as a history, current status, and future of addiction research and practice as we have come to understand it. The book “explores the prevention and treatment of such addictions as alcohol, tobacco, novel drugs, food, gambling, sex, work, shopping, the internet, and several seldom-investigated behaviors (e.g. love, tanning, or exercise),” says the introduction.

In the first chapter, co-written by Sussman, he makes a distinction between satisfying appetites and crossing over into addiction:

In many circumstances, satiation of appetitive needs serves highly adaptive functions. For example, one needs to eat food to live. If one does not obtain food, one will likely crave food and feel as if one will die without eating. (Eventually one will lose his or her appetite — and die.)

However, an illusory satiation of appetitive needs via a learned behavior may develop and become maladaptive (“addiction”). That is, one may experience satiation of a need that does not actually accomplish an adaptive goal. For example, if one suffers from alcoholism, one may feel the need to drink alcohol to live. … If one does not obtain alcohol, one may crave alcohol and feel as if one may suffer or die without drinking.

Another way of thinking about the difference between normal behavior and destructive, addictive behavior is the phenomenon of workaholism: Plenty of people put in long hours because they like their jobs and want to succeed. But does it dominate your waking hours? Can you compartmentalize?

“Work can be a passion,” Sussman says. “People love their job, and feel enthusiastic about it. But It can become a negative thing. Needing to work, catching that buzz off work. People who are compulsive workaholics actually start burning out because they work harder and harder and get less and less out of it.”

Sussman involved leaders in the field of substance and behavioral addictions research and practice to write for the textbook: There are 100 listed authors, including 16 from USC. Explored in this text include concepts of addiction, etiology, assessment, prevention, cessation, and future directions of addictions research and practice, considering neurobiological, cognitive, microsocial, and macrosocial and physical environmental levels of analysis.