The explosion in genetic research might leave some of us feeling that the important role of the environment is being ignored. EDIT Lab PhD students Daniel and Chris explain why recognising genetic differences is crucial if we want to understand the true role of the environment, and work out which environmental changes we can make to treat and prevent some of the most common and debilitating mental health problems.
Studying genes has helped us better understand the causes of many health conditions, predict people’s genetic risk, and improve treatment and prevention. But we know that most psychological traits reflect the influence of the environment as well as genes, and conditions like depression and anxiety are more environmentally driven. Sadly, studying environmental effects remains notoriously difficult. Each person has a vast set of unique experiences and exposures which are very difficult to measure reliably. The other big challenge is working out which ones directly increase our risk of developing conditions like depression or anxiety.
“if we want to understand how environments affect mental health, we need to recognise that genetic differences are always a hidden factor that could explain why some people struggle in environments where others don’t”
We also know genes and environments don’t work in isolation. Responses to the environment, like fear or learning, wouldn’t be possible without genes telling our cells to produce chemicals like adrenaline and dopamine. Differences in these genes can mean two people respond very differently to the same environment. Exposure to stress or trauma can also temporarily activate or deactivate certain genes involved in brain function, stress and immune responses.
All of this means that if we want to understand how different environments affect mental health, we need to recognise that genetic differences are always a hidden factor that could explain why some people struggle in environments where others don’t. One of the best examples is post-traumatic stress disorder (PTSD), which occurs exclusively after exposure to a traumatic event. While it’s normal to experience symptoms like hypervigilance or avoidance directly after a traumatic event, only around 1 in 6 people still experience clinically significant symptoms a year later. People’s risk of developing the long-term disorder can depend on other environmental factors, like previous adversity, social support and therapy, but much of the risk has also been shown to be genetic.
Genetic factors also affect our sensitivity to positive environments, including treatments. For conditions like depression and anxiety, no therapy or medication is effective for everyone. Many patients go through months or even years of trial and error before they find the right treatment, often experiencing worsening symptoms and increased hopelessness. Genetic research is already showing promise for getting people the treatment they need more quickly. One recent study of over 2,000 people taking the antidepressant Escitalopram found that genetic differences meant some people metabolised the drug too slowly or too quickly. This meant some didn’t get high enough levels in their blood to have any effect, whereas others had extremely high levels and experienced more severe side effects. Both groups were 3 times more likely than normal to switch to another antidepressant within a year. Findings like these could help clinicians improve treatment by prescribing the type and dosage of medication most likely to be effective for each person. There is already clinical evidence that tailoring medications based on genetics is more effective than normal prescribing. There is also preliminary evidence that genetic scores can be used to predict whether children with anxiety respond better to a high-intensity psychological treatment like individual cognitive behavioural therapy (CBT) versus a low-intensity treatment like group or parent-led CBT.
Genetically influenced traits can also affect which environments we’re exposed to in the first place, by making us select certain environments or evoke certain responses from others. Understanding these mechanisms can help us identify people at high risk of adverse experiences and intervene early to prevent worsening mental health. For example, we might find that children who study for longer end up achieving better grades and reporting less anxiety. On the other hand, a bit of anxiety about the outcome of exams can be a useful motivator. When worry about exams gets so high that it stops people from being able to focus, then it may be useful to engage in some type of therapy that addresses their anxiety. When this sort of intervention was tested, anxious children saw improvements not only in school performance but also in social adjustment.
Finally, childhood hyperactivity and impulsivity are highly heritable traits that can evoke harsh responses from parents, teachers and peers. These types of responses can further worsen children’s ability to control their behaviour, potentially leading to a vicious cycle of increasingly adverse interactions with others. Schools could improve children’s outcomes by identifying children with behaviour problems early, and taking steps to ensure they receive more understanding and support from parents, teachers and peers before problems escalate.
We’ve presented just a few examples of how recognising genetic differences allows us to better understand the incredibly complex puzzle of how environments affect our mental health. In turn, genetic research gives us unique insights into the kinds of environmental changes we can make to treat and prevent mental health problems more effectively.