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Abstract

Seasonal affective disorder (SAD) has generally been seen to be at the
extreme end of a continuum of seasonal variation to mood and associated
behavioural symptoms in the general population. SAD is currently categorised in the
DSM IV (American Psychiatric Association, 1994) as Seasonal Specifier, a type of
recurrent disorder, which may be applied to (non-seasonal) Major Depressive
Disorder (NSD). On the other hand, evidence is accumulating for SAD as a disorder
distinct from NSD. Hence the thesis investigates the nature of SAD in relation to the
seasonality of mood and behaviour in the general population. An epidemiological
survey was conducted by administering the Seasonal Pattern Assessment
Questionnaire (SPAQ) (Rosenthal, 1989) to Tasmanian Psychology 1 participants (N
= 502) showing up to 9% and 24 % may have SAD at clinical (C-SAD) and
subsyndromal (S-SAD) levels respectively. Statistical analyses on SPAQ variables
further confirmed the short day aetiology of SAD and also implicated metabolic
factors. Two longitudinal studies were conducted, each using three groups (control,
subsyndromal SAD, and clinical SAD) and six bimonthly testing sessions.
Participants were screened using the SP AQ and selected according to Rosenthal's
(1989) criteria. In each longitudinal study measures of depression, behavioural
symptoms and emotion were also obtained at each testing session. Longitudinal
Study 1 (n = 23 control, 21 S-SAD, and 18 C-SAD) investigated the proposition
that the symptoms of SAD may represent an increased parasympathetic or
decreased sympathetic arousal. Longitudinal Study 2 (n = 22 control, 21 S-SAD, and 17 C-SAD) studied cognitive processing across the twelve-month period. Digit
Span and Visual Memory Span subtests from the Wechsler Memory Scale
measured memory processes and a Mental Rotation task as well as verbal and
spatial versions of a Hemispheric Asymmetry Task determined cognitive efficiency,
spatial processing, and any differential hemispheric specialisation effects that may
be involved in SAD.
Distinctions between SAD and NSD were shown from the autumn/ winter
specificity of the atypical vegetative behavioural symptoms accompanying
decreases in mood and an underlying hypo-arousal showing similarities with
hibernation. Impairments to cognitive processing include deficits specific to the
spatial tasks that may have implications for differentiating between subsyndromal
and clinical levels of SAD and also in understanding vulnerability to SAD.
Implications for SAD theories are presented with findings indicative of dual
underlying mechanisms consisting of a seasonal component, as well as a depression
component in vulnerable SAD participants. Circannual rhythms were documented and several variables were shown to
vary with the seasons in control participants, thus extending current knowledge.

Item Type:	Thesis - PhD
Authors/Creators:	Austen, Margaret L.(Margaret Lyn)
Keywords:	Seasonal affective disorder
Copyright Holders:	The Author
Copyright Information:	Copyright 2003 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	For consultation only. No loan or photocopying permitted until 30/5/2005. Thesis (Ph.D.)--University of Tasmania, 2003. Includes bibliographical references
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