TORONTO - A group of Ottawa researchers has made some progress in solving the puzzle of why adolescents don't respond to antidepressants as well as adults.
Their work could help identify those depressed youngsters who will best respond to this medication.
The Ottawa group found adolescents with major depression can be classified in about equal proportions into three subgroups based on their parent's psychiatric history.
The researchers hypothesize that those depressed adolescents whose parents have a history of unipolar depression will respond to antidepressants while those with a family history of alcoholism or conduct disorder won't.
Targeting medication to responders could positively impact on personality development, school performance and the disturbing suicide rate among this age group, said Dr. Ian Manion (PhD), director of research in the department of psychiatry at the Children's Hospital of Eastern Ontario (CHEO).
He said "it's hit or miss" now whether antidepressants will work on adolescents. "If you're a family doctor and an adolescent presents to you with depression ... and you collect more information on family history, your comfort level in terms of prescribing antidepressants might be greater if you know that the patient fits the subgroup that has the greatest likelihood of a positive response."
While antidepressants have been proven effective in adults, they don't appear to work nearly as well in younger people. Dr. Manion used the figure of 72% for the response rate to serotonin reuptake inhibitors (SSRIs) in adults compared to only 35% in adolescents.
There is a number of possible reasons for this disparity. During adolescence, the neurotransmitter system is at a different stage of development. Depression in adolescence may also be a more virulent form of the disorder than that suffered by older patients.
"So there are some biological reasons, some neuro-psychological reasons and there may be some differences in the disorder itself," Dr. Manion said during the Ontario Psychiatric Association meeting here.
The depression seen in adolescence may be a "common pathway" for a number of different psychiatric illnesses later in life, he said. Or these adolescents may be misdiagnosed.
"We have a lot of adolescents who present with depressive features who may not have depression, so it's a misdiagnosis from the beginning," said Dr. Manion.
He added some of these teens may be suffering from conduct disorder, which is known not to respond well to antidepressants.
Dr. Manion and his colleagues at CHEO and at the University of Ottawa carried out a pilot study in which they categorized 13 adolescents with major depression into three subgroups according to the psychiatric history of their parents:
Based on the available literature on adults, the researchers believe that the pure depression group will benefit from treatment with an SSRI while the spectrum group won't respond. The "sporadic" patients will have a mixed response.
The researchers hope to carry out a multicentre, double-blind placebo-controlled trial of an SSRI to test this hypothesis.
In the current pilot project, 13 patients - 12 girls and one boy, aged 13 to 17 - were categorized into the subgroups. They had to have a score of at least 16 on the Beck Depression Inventory and completed structured interviews. At least one parent also had to participate. This last criterion might explain why researchers found it difficult to recruit subjects for the study, said Dr. Manion.
It was particularly difficult to get male patients to participate. Dr. Manion noted that males in general "avoid" mental health services. "Boys deny they have any psychological or psychiatric problems; that's classic."
The adolescents in the study were allocated in about equal numbers to the three subgroups. This differs significantly from similar studies of adults; in one, 92% of the adult subjects were classified as "pure depression" while only 8% fell into the equivalent "spectrum" category.
This difference in classification, noted Dr. Manion, may help explain the varying response rates to antidepressants. If a greater number of pure depression adults are entered into clinical trials of medications, and if the hypothesis holds weight, then it makes sense that their overall response rate would be higher.
While "pure" depression sufferers may derive optimal benefit from antidepressants, those adolescents with "spectrum" depression may be better off with other treatment approaches, including cognitive behavior techniques or group therapy, said Dr. Manion.
Adolescent depression is a common disorder. There are a number of "stressors" affecting today's generation of young people that go beyond normal school and peer pressures, said Dr. Manion.
"This next generation of adolescents will be the first that earns on average a lower income than their parents did. Usually it's the reverse. Education doesn't guarantee a job any more. The security and supports are not there and everything is being cut back. All of these things affect everyone, but more acutely those who are getting to the stage in their life where they have to make some major decisions."
Copyright © 1996 Maclean Hunter Publishing Limited
Reprinted with permission.
Internet Mental Health (www.mentalhealth.com) copyright © 1995-2011 by Phillip W. Long, M.D.