Recurrent depression is one of the
forms of major depression, where the depressive episodes occur at regular
intervals, with depression-free intervals between the episodes. Major depression is a mental health condition in
which feelings of sadness, frustration, guilt or other emotional responses
interfere with daily life for weeks or longer.
Findings of the study also show
that individuals whose major depression started before the age of 21 years
possessed a smaller hippocampus. However, individuals who had not suffered more
than one episode of major depression did not have a smaller hippocampus than
the healthy subjects.
The study was
conducted by ENIGMA
researchers which included a group of researchers from the Brain and Mind
Research Institute (BMRI) at the University of Sidney in Australia.
According to the
researchers, the study points to a need to treat depression
when it first emerges -
especially in adolescents and young adults.
The study examined magnetic
resonance imaging (MRI)
brain scans of nearly 9,000 individuals which
included 1,728 with major depression and 7,199 healthy individuals. The
researchers also had access to clinical records of the individuals with
Jim Lagopoulos, an associate
professor at the University, says the study gives new insights into the
mechanisms that might underlie depression.
"Despite intensive research aimed at identifying
brain structures linked to depression in recent decades, our understanding of
what causes depression is still rudimentary," Lagopoulos adds.
According to him, the first reason
we are not greatly aware of this is the lack of researches with sufficiently
large numbers of participants. Secondly, the disease and treatments vary widely
and there are also complicated interactions between brain structure and some of
the clinical characteristics.
Ian Hickie, co-director of BMRI,
says the clinical implications of the study results are that we should treat
first episodes of depression effectively.
"Particularly in teenagers and
young adults, to prevent the brain changes that accompany recurrent
depression," Hickie adds.
He points out that it also
important to conduct studies to find out methods to track changes in
hippocampus size over time in individuals with depression.
"Findings from such studies may
help explain the question of cause and effect whether hippocampal abnormalities
result from prolonged duration of chronic stress, or represent a vulnerability
factor for depression, or both," he suggests.
says that the BMRI research backs the "neurotrophic hypothesis of
depression," the concept that individuals with chronic depression have
certain differences in brain biology - such as sustained higher levels of
glucocorticoid - that reduce the size of the brain.
Psychiatry advance online publication 30 June 2015; doi: 10.1038/mp.2015.69