University of Toronto researchers analysed data from more than 1 100 Canadian adults with depression who were assessed every other year until they recovered, for up to 12 years.
"Our findings indicated that most people bounce back," study co-author Tahany Gadalla, professor emerita, said in a university news release. "Three-quarters of individuals were no longer depressed after two years."
There was, however, wide variation in how long patients took to recover, lead author Esme Fuller-Thomson, of the university's Faculty of Social Work, said in the news release.
"Early adversities have far-reaching consequences," Fuller-Thomson said. "The average time to recovery from depression was nine months longer for adults who had been physically abused during their childhood and about five months longer for those whose parents had addiction problems."
The study was published in the journal Social Psychiatry and Psychiatric Epidemiology.
Study co-author Marla Battiston added: "Numerous studies have shown that childhood abuse and parental addictions make individuals more vulnerable to depression. Our research highlights that these factors also slow the recovery time among those who become depressed."
The study did not determine why these childhood events are linked with slow recovery from depression, but the researchers suggested that these negative experiences might interrupt the normal development of a brain network involved in stress regulation.
Although the study found an association between childhood abuse, parental addictions and a person's vulnerability to slow recovery time from depression, it did not prove a cause-and-effect relationship.