Last week, I discussed how mental health conditions could all have one cause; one which can be inherited in a risk called the ‘p factor’.
But, there is more to the story than just genetics, environmental and psychological factors also play a key role. For example, child abuse, drug and alcohol abuse, and a traumatic experience such as being placed in warfare can also be a key contributor to susceptibility of developing a mental health condition.
Plomin and his colleagues have now attempted to quantify the genetic component of the p factor. From tests on 7000 pairs of twins – they estimate it’s heritability is approximately 55%. This means that genetic differences explain over half of the variation between people’s general susceptibility to metal health problems. The study also showed the stability of the p factor across someone’s lifetime.
Studies have now shown where these genes work. In 2018, Gandal and his colleague Dan Geschwind showed, from 7000 post mortems, that they control activity at the synapse. Another study by Hammerschlag backs this up. Her team investigated more than 7000 sets of genes with variants linked to five common mental health conditions, ‘almost all of these gene sets play a role in the synapse’ she says. So, to put it simply, the p factor effects communication between brain cells.
In a more recent study Maxime Taquet, from Oxford University, and his colleagues found that there is a ‘vulnerability network’ in the brains of children at high genetic risk of developing mental health conditions. They found differences in three key areas when comparing these to children with low genetic susceptibility: a structure called the default network (active whilst the brain is at rest), a structure involved in planning and control, and the part of the brain that processes vision. But how does having a brain with differences in these features influence an individual’s psychology?
Caspi and Moffitt (who have carried out a similar test to the one described above and found differences in a brain circuit crucial for monitoring and processing information so that it can be used in higher cortical functions such as regulating emotions, thoughts and behaviours) think that a high p factor probably manifests as a combination of disordered thinking, difficulties in regulating emotions and a tendency towards negative feelings.
So what has been done as a result of these breakthroughs so far?
Already, many drugs have been used for treatment of a variety of disorders; ‘antipsychotics, for example, have not only been used for psychosis, but also in mania, delirium, agitation and other conditions’ said Tova Fuller, of the University of California. The p factor makes sense of these ‘transdiagnostic’ therapies, but it isn’t ideal, as these drugs weren’t created with the p factor in mind.
But Gandal says that ‘if we can figure out the biology of the p factor, then it might be possible to target the mechanisms involved and develop therapies that work better across disorders. These could be given to a large number of patients, rather than treating each person based on their specific pattern of symptoms’.
Other than drugs, cognitive behavioural therapy (CBT) has also had transdiagnostic value. Currently, there are separate therapeutic guidelines for specific conditions. However the p factor may help clinicians to develop a one-size-fits-all approach to CBT called the common elements treatment to ensure that more people globally get the treatment that they need. Moffit doesn’t however disregard the need for specialists that help to treat, for example, schizophrenia.
Moffit also thinks that the existence of the p factor should shift a prompt from treating conditions themselves to treating the often distressing symptoms that people feel, and providing people with the tools to help themselves when issues arise.
Plomin also thinks that there is no boundary between mental health conditions, saying that he believes that ‘diagnostic guidelines are mostly a myth.’ He thinks that it ‘implies there are mentally ill versus the “normals”, really we’re all somewhere along a continuum.’