Inheritable genetic changes can help shape the mental health of coming generations
THROUGHOUT human history, people have realised that many illnesses are “in the blood”.
More recently, we have established that there is a genetic contribution to psychiatric diseases too. The extent to which the environment acts with our genes to cause illness is still under study, however.
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An even bigger question is whether the environment can cause inheritable “epigenetic” changes. These wouldn’t alter the sequence of your DNA one jot but instead leave chemical marks on genes that dictate how active they are, not just in you but in your children and grandchildren.
We know plants and fungi can inherit epigenetic changes and in this issue (see “Genes marked by stress make grandchildren mentally ill”), we report the best evidence yet that they are heritable in mammals too.
If male mice suffered from depression and social withdrawal because of maltreatment in the first weeks of life, so too did their pups and grand-pups even if they were well looked after from birth. Most tellingly, they bore the same chemical marks on their DNA as their maltreated forebears.
The mouse study is the first evidence that mental health problems can be “passed down” in this way. Evidence is growing, too, that exposure to environmental cues, from poor maternal diet during pregnancy to taking powerful recreational drugs such as cocaine, can and do alter the chemical markings on key genes that are linked with mental disorders such as bipolar disorder, schizophrenia and addiction.
“Environmental cues may alter chemical markings on key genes linked with mental disorders”
Many questions remain. For example, no one knows how many generations the “molecular memory” of epigenetic marks can persist for. Even so, the implications of this new understanding are huge.
The more we know about how genetic effects get passed down this way, the better we can help people make lifestyle choices with the potential to protect their children and even their grandchildren.
Of course, the science has a long way to go and converting basic knowledge into public health messages isn’t easy. The success of the campaign to reduce spina bifida with folic acid supplements shows that people will act on advice when lifestyle choices are linked to specific diseases. Imagine a similar dietary intervention that could reduce the risk of your offspring, and their children, suffering from depression.
Also, unlike genes themselves, which can only be altered through complex – and sometimes risky – gene therapy, epigenetic marks are reversible, and so could be a target for new, safer treatments.
Revealing how these marks work and what they do will open remarkable new chapters in genetics and health policy.
