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Thurston, Meghan Dory (2011) Individual differences in
anxiety in relation to inhibitory processes. PhD thesis,
University of Nottingham.
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For more information, please contact email@example.com Individual Differences In Anxiety In Relation To Inhibitory Processes Meghan Thurston BSc (Hons), MPhil Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy July 2011 Abstract When an individual perceives a situation or stimulus as anxiety-provoking they may react behaviourally; often actions are carried out that make it possible for the individual to cope with the anxiety. Thus, the individual comes to associate the elicited behaviour with a decrease in anxiety. Potentially, when such behaviours are carried out, conditioned inhibitors, or safety signals, are generated. On theoretical grounds, these are expected to help maintain and secondarily reinforce the behaviour. The current thesis examined both conditioned inhibition and the learning of stimulusÐresponse associations in both a healthy sample and a clinical sample of participants with anxiety disorder and/or problems with substance abuse.
Two novel tasks were developed and one previously used task was used to examine conditioned inhibition, Negative Images CI Task: Retardation Test,
Negative Images CI Task: Summation Test and ÔMission to MarsÕ CI Task:
Summation test respectively. Four response inhibition tasks were developed to examine any accuracy or reaction time differences to neutral and emotional stimuli: Emotional Stroop Task, Go/No-Go Words Task, Go/No-Go OCD Colour Images Task, Go/No-Go Black and White Images Task. Performance on all of the tasks was correlated with individual differences in anxiety as measured by questionnaires: HADS, MOCI, BIS/BAS and the EPQR-S. The results from the healthy sample tested showed clear evidence of discrimination learning, as well as conditioned inhibition as measured by both retardation and summation tests. There were also response inhibition differences on the Emotional Stroop, a classic Stroop effect, less accurate and slower for colour incongruent words compared to other word-types, and more accurate and quicker responses to negative and OCD related words. There were no response inhibition differences on any of the Go/No-Go tasks. Further to this, in general, individual differences in anxiety as measured by the HADS, MOCI, BIS/BAS and EPQR-S were related to performance on the tasks. The hypothesis was that individuals formally diagnosed with an anxiety disorder would show better i conditioned inhibition and response inhibition deficits. Recruitment for the clinical sample was unexpectedly difficult and therefore the sample size provides only preliminary data. The results from the clinical sample tested showed no difference in performance on any of the tasks; thus a formal clinical diagnosis of either an anxiety disorder or substance abuse disorder did not measurably impact on performance. However, overall the clinical group did not show discrimination learning or conditioned inhibition. On the Emotional Stroop Task the clinical sample showed a classic Stroop effect for accuracy and was also more accurate for negative words but there was no difference in latencies. There were no differences in performance on any of the Go/No-Go tasks. Across all of the tasks the clinical sample demonstrated a relationship between task stimuli and individual differences as measured by the HADS, MOCI, BIS/BAS and EPQR-S related to performance.
The results from the current tasks demonstrated that inhibitory processes are influenced or affected by individual differences in anxiety in a healthy sample;
in particular certain measures either positively or negatively influence performance. In order for this to be fully conclusive all of the tasks carried out need to be tested in a larger clinical sample. The results have implications for psychological treatments, for example, cognitive behavioural therapy (CBT).
CBT is based on associative learning principles, if safety signals were identified in the maintenance of the anxiety these could be incorporated into therapy and aid the breakdown of negative associations formed.
First and foremost I would like to acknowledge my supervisor, Dr Helen Cassaday, for her invaluable guidance, support and encouragement throughout my PhD. I would also like to thank Dr Hugh Middleton, the staff at KingÕs Mill Hospital and Oxford Corner for allowing access into their facilities to enable me to complete my PhD Studies. I am also grateful to my examiners, Dr Paula Moran and Dr Rachel Msetfi, for their discussion and insightful comments.
It has been a privilege to meet some wonderful friends and colleagues during my time at The University of Nottingham. A notable mention goes to fellow Canadian, Miss Karen Thur, who has shared the emotions of completing my PhD alongside me. Also, my two office mates Dr Romain Le Cozannet and Dr Cecilie Bay-Richter and to all my friends thank you all for making the experience unforgettable and enjoyable.
Lastly, I would like to thank my family. My Mom and Dad, Bubs and Fads, to you both I am forever indebted for your love and always believing in me. To my sister and future brother in law, Chels and TB, thank you for all the Facebook updates which constantly inspired me to keep going. To my husband, Alex, this PhD would not be possible without you, thank you for your love, support and just being you.
Behavioural Inhibition System/Behavioural Activation System BIS/BAS Cognitive Behavioural Therapy CBT Conditioned Emotional Response CER
Conditioned Stimulus, x refers to a number assigned to that CS CSx Diagnostic and Statistical Manual of Mental Disorders, 4th Ed.
DSM-IV EysenckÕs Personality Questionnaire Revised Short Version EPQR-S Exposure Response Prevention ERP Hospital Anxiety and Depression Scale HADS International Affective Picture System IAPS Increasing Access to Psychological Therapies IAPT Maudsley Obsessive Compulsive Inventory MOCI National Institute of Clinical Excellence NICE Obsessive Compulsive Disorder OCD
Anxiety disorders are debilitating and complex and although there are effective treatments the mechanisms that support such anxieties are poorly understood. It is widely recognised that many fears arise without any evidence that they have been learned. Nonetheless, cognitive behavioural therapy (CBT) which focuses on the un-learning of associations is a highly effective treatment for anxiety disorders. Watson & Rayner (1920) first demonstrated the role that classical conditioning can play and that fears and anxieties can be learned or acquired through this mechanism; a conditioned emotional response (CER). This occurred when a boy, little Albert, was shown white rat which was accompanied with a frightening noise. As a result of this pairing Little Albert cried and showed fear. It was also found that this response generalised to other white fluffy objects. CERs occur towards anxiety provoking or fearful situations. When faced with an aversive object or circumstance individuals often exhibit avoidance responses. These responses enable the individual to cope with the anxiety. One possibility is that the avoidance responses people make when fearful generate conditioned inhibitors (CIs), in this case safety signals (Gray, 1987), which prevent the excitatory response. Safety signals become negatively reinforced and secondarily rewarding. In the animal literature, CIs have been shown to be secondarily rewarding: rats Ôsigh with reliefÕ when given CI for shock (Soltysik & Jelen, 2005). This thesis will investigate whether individual differences in anxiety show particular sensitivity to CIs.
1.1 Anxiety, OCD and Panic Disorder 1.1.1 Description of Anxiety and Anxiety Disorders Anxiety is an emotion that arises to perceived fearful situations or objects. This can be a response which is temporary, state anxiety; the individual feels fear, 1 tension and apprehension towards specific situations. Or, it can be a more general tendency, trait anxiety; the individual has a predisposition to perceive a wider range of situations as threatening. In response to the perceived anxiety our bodies produce adrenaline to prepare for the fight/flight/freeze response (DSM-IV, 2000). Adrenaline causes physiological changes; these include:
increased heart rate, sweating, heavy breathing, shaking. The body is preparing to either fight, flight or flee the anxiety provoking and potentially harmful situation. Once in this situation typically these physiological changes decrease and so does the emotion/physical feeling of anxiety. However, for some individuals the anxiety and physical changes are overwhelming or are catastrophically misinterpreted that avoidance or safety behaviours develop.
Avoidance or safety behaviours include actions or thoughts to ease anxiety such that the individual can remain in and cope with the situation. When avoidance or safety behaviours start to interrupt and impinge on daily routines anxiety disorders develop.
Anxiety disorders cover a number of disorders where the primary feature is abnormal or even inappropriate levels of anxiety. They are highly distressing and disabling for the individual suffering from them. The anxiety that is experienced is an unpleasant emotion and as a result of avoidance and safety behaviours people often experience social isolation and often have to give up their social leisure and work. There are six major disorders: Obsessive Compulsive Disorder (OCD), Panic Disorder (with or without agoraphobia), Generalized Anxiety Disorder (GAD), Post Traumatic Stress Disorder (PTSD), Phobias including social phobia and Acute Stress Disorder (DSM-IV, 2000).
This thesis will concentrate on two main anxiety disorders: OCD and Panic Disorder.
1.1.2 Obsessive Compulsive Disorder OCD is characterised by the presence of either obsessions, compulsions or both. Obsessions manifest as intrusive and distressing thoughts or images causing an increase in anxiety, compulsions are often strict repetitive rituals or 2 habits that are performed and are intended to reduce anxiety (American Psychiatric Association (DSM-IV), 2000). Many healthy people experience distressing thoughts and repetitive checking (e.g. checking the stove to see if it is switched off more than once) but for individuals with OCD the obsessions and compulsions interfere with their daily life. They cause distress when intrusive thoughts occur and if compulsions are not carried out; the individual often recognises that their behaviour is unreasonable and excessive in nature (DSM-IV, 2000; Riggs & Foa, 1993). This degree of insight is important to the maintenance of the disorder (Foa & Kozak, 1995) as this has implications for treatment outcomes. The individual needs to be able to recognise that these behaviours are excessive in order to address them in treatment. Onset typically begins in the early 20Õs, with some studies showing that age of onset is slightly earlier for males than for females (Lensi et al., 1996). The prevalence of OCD is approximately 2.5% in adults in an American sample (Reiger et al., 1988), although this varies due to geographical location (ranging from 2.5% in German and American samples, to 0.4% Taiwanese sample, Weissman et al., 1994). Prevalence rates have also increased over the past years from 0.05% in the 50Õs (Rudin, 1953) to 2.5% in the 80Õs (Reiger et al., 1988). These prevalence rates are from different samples and countries so the figures need to be considered with respect to geographical variation; however the increase does suggest a rise in incidence. This could be due to either an increase individuals suffering with OCD, an increase in public awareness, or a better understanding of how to detect OCD. Prevalence rates do not differ across gender, in other words the frequency with which OCD is diagnosed does not vary between males and females (Nestadt et al., 1994).
Individuals with OCD exhibit and can engage in a range of obsessions and compulsions to control their anxiety and it has been suggested that there are multiple symptom subtypes of OCD which vary by gender; men report more sexual and exactness obsessions whilst women report more aggressive and cleanliness obsessions (Lensi et al., 1996). Although no one standard taxonomy model has been identified many have been suggested with the number of subtypes ranging from four (Leckman et al., 1997; van Oppen et al., 1995) to
seven (Calamari et al., 2004). The common subtypes are: