Wearables and mHealth in mental health and neurological disorders.

According to the World Health Organization, neuropsychiatric conditions account for up to one third of years lived with disability among adults worldwide (Chisholm 2015). In addition, it is estimated that almost 50% of adults will develop at least one mental illness over their lifetime (Center for Disease Control and Prevention 2011). Mental health diagnosis, and (to a large extent) neurological disorders, still rely on traditional subjective clinical evaluation performed using standardized scales, manual review of in-clinic recordings, or detailed face-to-face interviews.
 
 With the recent increase in proliferation of wearable sensors and mobile health applications ('mHealth apps') there has been a rapid increase in the number of tools that aim to assess mental health and neurological disorders in a more objective and a more frequent way, particularly targeting the monitoring of the individual in their home environment. However, this explosion of devices and tools producing self-monitored 'Big Data' brings with it an increase in bias and variance, which is dependent on the user and their devices. Notably, very few of the existing applications have been rigorously validated. There is therefore a large interest in the field for designing novel evidence-based applications that will support the diagnosis and management of mental health and neurological disorders.&#13.