## A Virus May Be a Trigger for Depression in Later Life
A Japanese research team has discovered that an infection with a particular virus during infancy may be a trigger for depression in later life. This finding challenges the long-held belief that inherited genes are the primary cause of depression.
The team, from the Jikei University School of Medicine in Tokyo, published their findings in a U.S. science journal in February. They had previously announced in 2020 that SITH1 proteins, produced by the human herpes virus type 6 (HHV6), play a role in developing depression.
HHV6 is a common virus that causes exanthema subitum, a childhood illness characterized by a fever. Almost everyone is infected with HHV6 during infancy and carries the latent virus throughout their life.
When a person with the virus feels run down, HHV6 becomes present in saliva and can spread to the brain, causing reinfection and producing SITH1 proteins. The research team found that individuals with SITH1 proteins are more prone to developing depression than those without.
Through experiments involving mice, the team also determined that reinfection of brain cells plays a role in the development of depression.
one that easily produces the protein and one that does so with difficulty. The study found that 68% of 28 patients with depression were infected with the type that easily produces SITH1, compared to 29% of 35 healthy individuals.
Interestingly, 47% of patients with depression infected with the easily-producing type of the virus had family members with depression. This suggests that the virus transmitted from the mother to the infant, rather than the mother's genes, may make the child prone to depression.
Professor Kazuhiro Kondo, a member of the research team, believes that uncovering the mechanism behind this link between the virus and depression could lead to new solutions for preventing and treating the condition.