In this book the authors use a 'multi-disciplinary' approach to mental illness and claim to have discovered a 'new causal theory'. However, the causes they uncover are far from revelatory. The main conclusion of the book is that stress causes illness (mental and physical), and stress, in turn, is caused by 'deprivations' in 'personal agency'. Therefore, the key concept of their theory is 'personal agency' and the pivotal role this has in psycho-social well-being.
The reason I say this is not 'original' is because it is something from 'perennial philosophy'. While, the authors refer mainly to contemporary sources, similar ideas about personal agency may be found in many places - including, I believe, in the sayings of Jesus and the Buddha. However, perhaps personal agency is most deeply examined in the areas of freewill and responsibility, and in writings in the Existentialist tradition.
The authors' claim to originality lies in their break from the previously dominant physical-reductionism of the 'medical model'. While that would explain everything, 'bottom up', in terms of chemical 'imbalances', the authors detail a top-down, information systems, cybernetic approach. More than once they point to the inclusion within their model of the 4 Es model of cognition as embodied, embedded, enactive and extended.
However, I believe the authors ultimately fail to break with the materialist tradition. For them the individual's 'failure to achieve agency' is conceptualised purely in terms of external causes. Many such external determinations are cited: unemployment, poverty, abuse, trauma, lack of education, lack of social recognition, political repression. The basic assumption is of an external cause acting to 'prevent' personal agency. This assumption is never questioned, and operates throughout the authors' argument.
But can the assumption of external causality be questioned? Since this is a book review, I do not want to get too much off topic, so I'll be brief.
I am in agreement with the authors, that agency is crucial to mental health. This argument can be found stated very simply in William Glasser: the failure to 'meet one's needs' is the cause of mental illness. The disagreement I have with the authors lies in the power that the individual has to 'assert their agency'. While the authors see the disempowered sufferer as fundamentally passive, Glasser, and I, would disagree.
Can a person's sense of agency ever really be prevented externally? No, because no matter how powerless a person is, they can still choose their actions. Agency is inseparable from freewill, and as Carl Rogers said, 'freewill is real if we choose to use it'. This modest ability may not seem much, but choice is the essential component of human agency.
To my thinking, conceiving personal agency without this foundation, as the authors do, unconsciously re-inscribes the 'mechanistic thinking' they rail against.