The reference book Emotional Addictions proposes that some people may actually be "addicted" in an unhealthy manner to specific emotions. The emotion could be anger, anxiety, apathy, egotism, envy, guilt, jealousy, resentment, revenge, or self-hatred. Historically, one of the greatest challenges to both mental health and substance abuse counselors has been the addict who has been clean and sober for some time, yet still has substantial difficulties coping with life. Ladd contends that emotional addiction operates under similar criteria to a physical addiction, with both forms of addiction showing characteristics of denial, compulsive behavior, dependency, tolerance, addictive thinking, and withdrawal symptoms. By combining emotions with addictions, Ladd has written a cutting-edge approach to helping people with addictions and mental health problems.