A Virus May Be a Trigger for Depression in Later Life
A research team from the Jikei University School of Medicine in Tokyo has made a groundbreaking discovery about the potential cause of depression. Their findings, published in a U.S. science journal in February, suggest that an infection with a particular virus during infancy may be a trigger for depression in later life.
This discovery challenges the long-held belief that inherited genes are the primary cause of depression. The team's previous research in 2020 identified SITH1 proteins, produced by the human herpes virus type 6 (HHV6), as playing a role in developing depression.
HHV6 is a common virus that causes exanthema subitum, a childhood illness characterized by a three-day fever. Nearly everyone is infected with HHV6 during infancy and carries the latent virus throughout their life.
When a person with the virus experiences stress or illness, HHV6 can become active again. The virus spreads from the mouth to the nose and then to the brain, causing reinfection and producing SITH1 proteins. Individuals with higher levels of SITH1 proteins are more prone to developing depression than those with lower levels.
The research team conducted experiments on mice to further understand the mechanism of depression development. They found that reinfection of brain cells with HHV6 plays a crucial role.
one that easily produces the protein and one that does so with difficulty. The researchers discovered that 68% of 28 patients with depression were infected with the type that easily produces SITH1, compared to 29% of 35 healthy individuals.
Interestingly, among patients with depression infected with the easily-producing type, 47% had family members with depression. This suggests that the virus itself, rather than the mother's genes, may be the factor that makes the child susceptible to depression.
"When we uncover the mechanism, we can also find solutions," said Professor Kazuhiro Kondo, a member of the research team. This discovery opens up new avenues for understanding and potentially preventing depression, offering hope for millions of individuals struggling with this debilitating condition.