Abstract
Background
Depression is pervasive worldwide and a leading cause of disability. Alongside mood
symptoms, cognitive impairment is a common feature of depression and is linked to poor
functional outcomes. Impaired cognitive functioning is particularly prevalent in those
hospitalised with depression, and often persists even with resolution of mood symptoms.
Current inpatient treatment in Aotearoa New Zealand focuses on safety and crisis
stabilisation, primarily with the use of medication. Given the prevalence and severity of
cognitive impairment in the depressed inpatient population, and the inadequacy of current
treatment to address cognitive impairment, there is a need for the development of novel
interventions. With this in mind, Activation Therapy (AT) was developed, combining
psychological therapy (Behavioural Activation) and cognitive remediation (Cognitive
Activation).
Objective
The main objectives of this thesis are:
• to describe the baseline profile of cognitive impairment in the depressed patient
sample,
• to investigate cognitive functioning outcomes following the AT treatment
compared to TAU, and
• to investigate potential predictors of cognitive change following treatment.
Methods
This thesis describes a randomised controlled trial, comparing an intensive course of AT
with treatment as usual (TAU). Eighty-two inpatients with a primary diagnosis of Major
Depressive Episode (unipolar or bipolar) were recruited into the study along with 61
healthy control participants. Depressed patients were randomised to receive a two-week
course of either AT or TAU. Patients completed measures of cognitive functioning, general
functioning and mood at baseline and at 14-week follow-up.
Results
Key findings were:
• At baseline, the depressed inpatient group demonstrated significantly impaired
cognitive functioning compared with healthy control participants across the full
range of cognitive tests and domains.
• Despite large overall group differences, at an individual level, cognitive functioning
varied within the depressed inpatient group, ranging from ‘not impaired’ to
‘severely impaired’.
• At 14-week follow-up the AT treatment arm improved significantly more than the
TAU treatment arm in the verbal learning and memory domain.
• At 14-week follow-up, for study completers only, the AT treatment arm
additionally improved more than the TAU treatment arm for executive functioning
and attention.
• There were no significant differences between treatment arms for global cognition,
visuospatial learning and memory, psychomotor speed or subjective cognitive
functioning following treatment.
• Age and domain-specific baseline cognitive performance were consistently
associated with cognitive change over time, with younger age and poorer domainspecific
baseline cognitive performance associated with greater improvement at 14-
week follow-up.
Conclusions
The AT study is unique in two key aspects: 1) the inclusion of a severely depressed
inpatient sample, which has rarely been examined in the cognitive remediation field; and 2)
the AT intervention, in the combination of cognitive remediation with a psychological
therapy, which few study interventions incorporate, as well as the AT intervention’s
intensity and short duration. Findings from the current thesis suggest that AT improves
cognitive functioning more than TAU in some domains but not others. Predictor analyses
suggested that younger individuals with greater cognitive impairment may benefit most, at
least within an inpatient setting. The remediation of impaired cognitive functioning in
depression, including the identification of those who may benefit most, remains an area
warranting further research focus.