New Depression Model Advances Disease Frontiers

Nov 06, 2006, 00:00 ET from Centre for Addiction and Mental Health

    TORONTO, Nov. 6 /PRNewswire/ - A new study released today by the Centre
 for Addiction and Mental Heath (CAMH) provides a thorough explanation of
 how the "chemical imbalance" occurs in major depression, a disease that
 impacts approximately 5% of people globally. For over 30 years, scientists
 believed that monoamines -- mood-related chemicals such as serotonin,
 norepinephrine and dopamine -- are low in the brain during major depressive
 episodes. This is commonly referred to as a "chemical imbalance". However,
 no one had ever found a convincing explanation for monoamine loss, until
     Led by CAMH's Dr. Jeffrey Meyer, this study published in the November
 Archives of General Psychiatry investigated whether brain monoamine oxidase
 A (MAO-A) -- an enzyme that breaks down chemicals like serotonin,
 norepinephrine and dopamine -- was higher in those with untreated
 depression. The results showed that in major depression MAO-A was
 significantly higher in every brain region that the scientists
 investigated. On average, MAO-A was 34% higher.
     According to Dr. Meyer, "In major depression, higher levels of MAO-A is
 the primary process that lowers monoamine levels. Having more MAO-A leads
 to greater breakdown of key chemicals like serotonin."
     This study includes a detailed new monoamine model of depression, based
 upon this work as well as four previous publications from Dr. Meyer and
 collaborators at CAMH.
     Said Dr. Meyer, "A key barrier to making advances in treating
 depression is a lack of precise disease models. Having disease model is
 like having a map. Once you have that map you can really begin to
 understand how an illness like depression works, and offer more targeted
 and effective treatment."
     A second part of this new model is that monoamine transporters have an
 important role in removing monoamines away from active sites. Having more
 of a monoamine transporter is not helpful as it removes more monoamine --
 for example if one has more serotonin transporter, one would additionally
 lose more serotonin during depression.
     "An important aspect of our advanced monoamine model is that
 individuals with depression lose chemicals like serotonin and dopamine at
 different rates based upon transporter density. This helps explain why one
 person with depression may experience loss of appetite while another may
 not. And some people have more severe symptoms than others," said Dr.
     This advanced monoamine model of depression is a huge step forward in
 the disease frontier. It brings the study of mental illness closer to the
 advancements seen in research into physical illness such as cardiac
 disease, and offers one of the most comprehensive disease models in mental
     The next step for researchers will be to investigate why MAO-A levels
 are raised in the brain and consider prevention strategies. Prevention
 strategies are critical -- according to the World Health Organization,
 major depression is currently the fourth leading cause of death and
 disability and is expected to rise to second by the year 2020.
     To view a diagram, visit Monoamine Model of Depression
 More information on this field of study is available at Background
     The Centre for Addiction and Mental Health (CAMH) is one of the largest
 addiction and mental health organizations in North America and Canada's
 leading mental health and addiction teaching hospital. CAMH is a Pan
 American Health Organization and World Health Organization Collaborating
 Centre, and is fully affiliated with the University of Toronto. CAMH
 combines clinical care, research, policy, education and health promotion to
 improve the lives of people impacted by mental health and addiction issues.

SOURCE Centre for Addiction and Mental Health