Robert Plomin has spent the best part of the last half-century unpicking the Nature vs Nurture debate. Ever since Freud, public opinion has strongly leant towards the assumption that most of our psychological traits, including personality, psychopathology and school achievement, are largely a result of 'nurture'. Plomin's conclusion after decades of research is the opposite: our psychological traits are highly heritable, and the role that the environment plays in our psychological development is both minimal and unpredictable.

The first half of Blueprint recounts his early research using twin and adoption studies, which not only confirmed that genetics is the major systematic influence on our psychological character, but also overturned many of the prevailing assumptions about how our genes and environment interact. One of the most interesting truths to emerge from his research is about 'the nature of nurture'. What we might think of as environmental effects on our personality are actually influenced by genetics – our inherited personality determines how we perceive events and this in turn shapes their impact on us. Another finding, which is important for us as clinicians, is that 'the abnormal is normal'. There are no single genes that determine whether someone will have, say, an intellectual disability or mental illness. What matters is how many implicated genes we have, which is normally distributed throughout the population. This means that what have previously been conceptualised as diagnosable disorders are actually just the extreme ends of a continuous scale.

Latterly, the advances in genomics have allowed Plomin and his colleagues to hunt for the exact DNA differences that contribute to our individuality, which add up to a polygenic score for a particular trait such as schizophrenia. Whilst the single nucleotide polymorphisms (SNPs) discovered do not yet account for all the heritability of psychological traits, Plomin insists that it is only a matter of time. Plomin is a self-confessed optimist, and is excited about the potential benefits of knowing what our psychological strengths and weaknesses are. He anticipates not only individually tailored treatments, but preventative interventions targeted at people who are predisposed to certain problems. However, for those who are more genetically “glass half empty” than he is, there are plenty of reasons to worry about how such information could be misused.

Blueprint is not as easy a read as many other medical books on the shelves at the moment. There are no heart-warming or dramatic anecdotes to draw you in emotionally, and Plomin has a tendency for self-repetition which I found grating. However, he writes clearly on a difficult and very important topic. As Plomin rightly points out, the public needs to be DNA-literate, because “the genome genie is out of the bottle and, even if we tried, we cannot stuff it back in”.