I-Phone now provide the facility for users to complete the PHQ-9 and GAD-7 and get feedback on the results https://support.apple.com/en-gb/guide/iphone/ipha8d27408f/ios. They caution that the results only indicate the ‘risk’ of developing anxiety (measured by GAD-7 score if over 13) and depression (measured by PHQ-9 score if over 18). But they provide no quantification of the ‘risk’. The I-phone suggests that those with PHQ-9 scores of 10 or more or GAD-7 scores of 8 or more should consult their GP/Specialist. If only a small proportion of the 1.5 billion I-phone users did this, it would likely overwhelm front-line services, crowding out those who do really need a clinician’s help.
Most people appreciate that every drug has a side effect. But what is not appreciated is that a psychometric test, administered in isolation, has serious adverse consequences – false positives, for every person correctly identified between 1-4 other people are mislabelled and likely mistreated. I explain how this comes about at the. end of this blog. Suffice it to say for now that there is no evidence that scores on these tests, administered without specification of context, predict anything. Scores can be high for myriad other reasons, than depression or anxiety, e,g exam results, strained relationship, housing disrepair, disorders other than anxiety or depression. For example, a just published study on bulimia in Japan, found a quarter were suffering from depression. The public are likely to dismiss the smallprint about ‘risk’ because of a lack of understanding, unwittingly creating a ‘mental hypochondria’. But don’t worry, before long Apple will develop an App for measuring this construct, despite it lacking any validity. The results can then be easily integrated into AI generated therapy. It is no wonder that Illinois has already banned AI Therapy.
Tests are very good on sensitivity, i.e they identify the vast majority ( about 90%) of people who have a disorder. The downside is that they have poor specificity (about 60%),correctly identifying barely half of those who do no t have the disorder. Imagine a 100 people are assessed with a ‘gold-standard’ diagnostic interview, it will likely identify 10 of them as being depressed (top left hand column below) and 90 as not having depression (top right hand column below).Those who do not have a disorder are far more numerous those who have a disorder. Applying the test to column one, 9 out of 10 would be above the cut-off and 1 below. Moving now to the 2nd column, the 90 people who do not have the disorder, the test only gets 60% of these right, ie 54 people, and gets 36 people wrong. Thus there are 9 people that the test got right versus 36 people that it got wrong, thus for every person it got right, it got 4 wrong.
Imaginary Sample of 100 clients
| Depressed n=10 | Not depressed n=90 |
| Above the cut-off n=9 | Above the cut-off n=36 |
| Below the cut-off n=1 | Below the cut-off n=54 |
The adverse consequences of the test are that approximately 4 times as many people are screened positive as have the disorder. Thus by itself the test would lead to rampant invasive treatment. Using the analogy of breast screening many more tests would be conducted before surgery or chemotherapy. However with the sole test used in NHS Talking Therapies there are no such checks and balances.
When the PHQ-9 and GAD-7 have been evaluated alongside a diagnostic interview, the tests give a prevalence rate two to three times higher. Patients with principal diagnoses of post-traumatic stress disorder, obsessive compulsive disorder, specific phobias and adjustment disorders commonly score above thresholds on these tests. So that when these tests are reified the test completer Is nudged in the wrong treatment direction,.
Completing these tests fits neatly into the time slot of the typical GP consultation time of 10-15 minutes. Psychological therapists will likely not see the use of the I-phone in the therapeutic hour as too burdensome, conferring a ‘scientific glow’ to proceedings, even if they do not know what they are measuring.
Using the PHQ-9 the natural recovery rate for depression amongst GP patients administered an antidepressant was 47% within 3 months [Moore et al (2012)]. So that ‘watchful waiting’ is probably best in the 1st instance , waiting for the Storm to pass rather than heading into the eye.
Dr Mike Scott