| Popis: |
Epidemiological studies suggest a high prevalence of depression in those who have experienced trauma and abuse in childhood. The aim of this thesis is to investigate the functional mechanisms of altered emotional processing that play a mediatory role in this causal relationship between childhood trauma and depression. From the perspectives of different scientific disciplines - psychophysiology, neuroendocrinology and behavioural psychology- emotional resilience and vulnerability to depression were investigated in order to consider different developmental pathways to psychopathology. A total of 83 participants (29 male: 54 female) were recruited for this project. Emotional processing styles were concurrently examined using three different experimental measures, namely startle responses to emotional images (Experiment 1), cortisol responses to emotional images (Experiment 2), and facial emotion recognition (Experiment 3). These measures were undertaken in a cross-sectional study comprising four groups: healthy individuals with (N = 17) and without a history of childhood trauma (N = 24) and depressed patients with (N = 23) and without a history of childhood trauma (N = 19). All the experiments were conducted at the same day and with the same order (Experiment 3 follows Experiment 1) for each participant. During those experimental sessions saliva samples were collected to measure cortisol levels for Experiment 2. Mediation analyses were conducted to examine possible roles of emotional processing styles examined in these experimental measures mediating the relationship between childhood trauma and depression. Experiment 1) demonstrated strong normal affective startle modulation in healthy abused individuals contrasting with its absence in depressed individuals. Experiment 2) demonstrated lower cortisol reactivity to emotional images in those with a history of abuse but no differences between healthy and depressed abused individuals. Experiment 3) demonstrated more errors in recognising negative facial emotions but fewer errors on positive facial emotions within healthy abused individuals relative to healthy non-abused individuals. An opposite pattern of more errors in recognising positive facial emotions but few errors on negative facial emotions was found within depressed abused individuals relative to depressed non-abused individuals. The results from the mediation analyses found that suppressed startle amplitudes mediated the relationship between childhood trauma and depression and were a marker of vulnerability to depression, whereas the absence of this marker was associated with resilience to depression. However, the same analyses on cortisol reactivity and facial emotion recognition did not demonstrate significant mediation in the relationship between childhood trauma and depression. The results of the study suggest that the retention of a normal affective startle modulation and the development of a positive bias in the recognition of facial emotions are implicated as functional mechanisms that render abused individuals resistant to depression. Reduced cortisol stress reactivity, that may reflect adrenocortical abnormality, was found in abused individuals. The identification of these cognitive resilience factors that may be able to compensate for long-lasting effects of childhood trauma has important implications for the future design of the psychological treatments targeted specifically at the patient population with a history of childhood trauma. |
