What incidence actually counts

1. Incidence counts new cases appearing over a set period, so it is not the same as the total number of people living with a condition at one moment.
2. Every figure you meet is a recorded incidence, meaning the number of cases that reached a doctor, a survey or a hospital and were written down.
3. The recorded incidence of unipolar depression and of addiction has generally risen in the UK across recent decades.
4. Saying the figure has risen and saying the problem has grown are two different claims, and only the first one is safe.

Why the recorded figure changes

1. Classification changes, because each revision of the ICD redraws the boundaries of a diagnosis and decides what counts.
   1. Internet addiction is a clear case, since Young worked with clients at a centre for online addiction in 2007 on a problem that simply did not exist in earlier records.
2. Reporting changes, because as stigma weakens more people go to a GP about persistent low mood or about their drinking.
3. Detection changes, because GPs and other professionals are now more likely to ask about mood or substance use during an appointment and to record what they find.
4. Law and policy change, because the law and official attitudes decide how mental health problems are treated and how willing people are to come forward.
   1. Where help can be accepted voluntarily rather than imposed, more people come forward and more of them appear in the figures.

Why the underlying problem may genuinely change

1. Part of the change may be real, because the conditions people live under are not fixed from one generation to the next.
2. Caspi and colleagues found in 2003 that stressful life events predicted depression, particularly in people carrying a short version of the 5-HTT gene.
   1. If a generation lives through more stressful events, that finding suggests genuine incidence of depression could rise rather than only the recording of it.
3. For addiction, what is available matters, because a substance or activity that becomes easier to reach can be used by far more people.
   1. Internet addiction could not have existed before home internet access was widespread, which shows availability creating a genuinely new pattern of dependence.

Why the figures are hard to trust

1. There is no single national count, so figures come from GP records, from surveys and from hospital data, each covering a different slice of the population.
2. Self-report sits at almost every stage, and self-report invites social desirability, which is exactly the weakness identified in the outcome questionnaire used by Young in 2007.
3. People may under-report how much they drink or use, so the recorded incidence of addiction is likely to sit below the true figure.
4. Many people with depression never see a doctor at all, so those cases never enter any record.

Turning this into marks

1. For an explain item give one reason plus the reasoning that connects it to the figure going up, rather than two bare reasons.
2. Name a mechanism rather than a mood, so write that broader ICD categories captured more cases instead of writing that people are more stressed now.
3. The mark most often lost is answering generally about mental health when the question names depression or addiction.