Student: Nicole Coman-Wright
Supervisor: Claire Dowson
Sponsor: New Zealand Federation of Graduate Women
In general practices, increasing numbers of people are prescribed Fluoxetine (an antidepressant) as a maintenance treatment to prevent recurrence once they have recovered from an episode of depression. Fluoxetine is a selective serotonin reuptake inhibitor or SSRI, which causes an increase in levels of serotonin in the brain. There are suggestions that SSRIs may impair cognitive function such as thinking, memory and concentration as well as affecting behavioural function. No studies to date have considered the effects of remaining on Fluoxetine once a person has recovered from an episode of depression. Prompting the development of the “Cognition and Behavioural Function in Long Term SSRI Antidepressant Use” study or Cognition & SSRI study which is currently underway in the Department of Public Health and General Practice. This report refers to the Control (comparison) Group part of this study.
The “Cognition & SSRI” study aims to determine the effect on cognitive and behavioural functioning from continued antidepressant use in previously depressed but currently well people. This will be done by way of a major 18 month Randomised Controlled Trial “The Antidepressant Cessation Trial”. The trial involves comparing cognitive and behavioural functioning, side effects and symptoms of depression in two groups of participants, with one group currently taking Fluoxetine while the other being tapered from their current Fluoxetine treatment to a placebo. Both participants and researchers are blinded as to who is taking placebos or Fluoxetine.
My role was to recruit and to conduct computerised assessments for the control (comparison) group. This involved recruiting people aged between 18 and 75 years, who have never taken antidepressants and do not currently consider themselves depressed, to participate in a control group. Their gender, education and ethnicity were recorded to be used as descriptive data to determine compatibility as a comparison group. The Montgomery Asberg Depression Rating Scale (MADRS) is a self report measure of current depression and was used to screen participants before commencement of the computer test. The control group participants were instructed to use the CANTABeclipse program to complete a 45 minute computerized cognitive test panel comprising 6 tests. The tests examine participant’s ability to retain spatial information, manipulate remembered items in working memory, comprehension, visual memory, new learning and reversal. Of particular interest is frontal lobe dysfunction which has been associated with use of SSRIs in some studies. The tests involved are sensitive to changes to the fronto-striatal areas of the brain, measure frontal lobe, parietal lobe and ‘executive’ dysfunction, and are also a sensitive measure of general performance.
Demographic groups and MADRS scores were compared to determine any differences in CANTAB scores within the control group. The control group comprised 62 people with 66% being female. 85% participants identified with being New Zealand European and 1.6% Maori. The group’s average (mean) age was 42.81 and had an average of 15.24 education years and an average MADRS score of 4.56 (not indicating depression). In order for the control group’s CANTAB scores to be compared with the groups in the “Cognition and SSRI” study both the demographics and MADRS scores of participants must be comparable. At present the average age of the control group is lower than that of the main study group.
Analysis within the control group showed an association between age and performance, meaning that with increased age there is a reduction in ability to perform cognitive tasks, with younger people having higher (better) scores. This was expected as the CANTAB tests rely on motor function which deteriorates with age and are not dependent on past learning or other aspects assessed in standard intelligence tests. No other factors (gender, occupation, education years, MADRS) appear to affect participants’ performance on the tests.
Overall interim analysis indicates that the control group is younger than the current main study group but comparable on gender, ethnicity and education, therefore we will need to recruit further older participants for controls. People are still being recruited for the “Cognition and Behavioural Function in Long Term SSRI Antidepressant Use” study. We will continue to recruit control group participants comparable in age and gender to the main study.