A research team used MRI scans to measure combined hippocampal volume in people when they were first diagnosed with schizophrenia, before they had taken anti-psychotic medication. The same people were scanned again after five years of regular anti-psychotic medication. A comparison group without a diagnosis was scanned at the start of the study.
| Group and time of scan | Mean combined hippocampal volume (cm³) | Range of individual volumes (cm³) |
|---|---|---|
| People with schizophrenia at first diagnosis, before medication | 6.5 | 5.8–7.4 |
| The same people after five years of regular medication | 6.2 | 5.5–7.1 |
| Comparison group without a diagnosis | 6.9 | 6.0–7.7 |
The researchers concluded that reduced hippocampal volume causes schizophrenia and that hippocampal volume can be used to determine whether an individual has the disorder.
Using the data in the table, outline one weakness of each of the researchers' conclusions.
144 exam-style questions on OCR GCSE Psychology 3.2 Theories/Explanations, covering 3.2.1 Clinical characteristics of schizophrenia, 3.2.2 Key statistics of schizophrenia, 3.2.3 Dopamine hypothesis of schizophrenia, 3.2.4 Brain structure and function in schizophrenia; criticisms, 3.2.5 Social drift theory of schizophrenia, 3.2.6 Schizophrenia research study: Daniel et al. (1991), 3.2.7 Clinical characteristics of clinical depression, 3.2.8 Key statistics of clinical depression, 3.2.9 Social rank theory of clinical depression, 3.2.10 ABC Model of clinical depression, and 3.2.11 Clinical Depression research study: Tandoc et al. (2015). Each one has a worked solution and a mark scheme showing where the marks go.