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The Internalizing and Externalizing Pathways to Addictive Behaviours

An addiction is a maladaptive pattern of behaviour characterised by preoccupation, increasing tolerance, using for effect, using alone, using more than planned, withdrawal and inability to reduce the behaviour which can lead to functional impairment and distress. It is now widely accepted that the use of the term addiction is not merely restricted to drugs and alcohol but can also apply to food, sex, gambling, shopping and internet usage. These addictions frequently occur together in the same individual. There are many biological, social and psychological factors that are associated with addictive behaviours and personality has a large role to play. Personality can be described as how we differ individually “in characteristic patterns of thinking, feeling and behaving” consistently over time and personality disorders are when these thoughts, feelings and behaviours “significantly and adversely affect how an individual functions in many aspects of life”.

Both personality disorders and non-clinical traits tend to co-occur in certain patterns and as early as 1945 Horney described the two most common domains of psychopathology in children and adolescents. Horney described children who “move away from the world” (internalizing) and “move against the world” (externalizing) and these two dimensions have long been suggested as a possible model for understanding this comorbidity pattern. These dimensions of internalizing and externalizing disorders have been replicated in numerous studies and research has also suggested that there is a strong genetic component underlying these dimensions. Chan, Dennis and Funk also suggest that these disorder types tend to share aetiology, consequences, treatments and outcomes.

Internalizing disorders usually involve negative affect (anxiety, depression etc.) and inhibition and are associated with difficulties in controlling emotions. These disorders usually have a later onset in life and their prevalence increases with age however, some research has found that they do exist in childhood and adolescence. Externalizing disorders usually involve disinhibited personality such as low constraint and conscientiousness and elevated impulsivity and sensation-seeking. The externalizing disorders are associated with difficulties in controlling behaviour and tend to have an onset in childhood or adolescence with their prevalence usually, but not always, decreasing with age. Both internalizing and externalizing disorders can be associated with negative affect however it seems that only externalizing disorders include disinhibition.

Research suggests a close association between personality disorders and addictions and therefore, on the basis of the dimensional model of personality disorders it can be expected that there is also an association between subclinical levels of maladaptive personality and addictions. For example, Carlotta et al. found strong associations between Gambling Disorder and low scores on the Five Factor Model scales of Openness and Conscientiousness which are non-clinical personality traits. The relationship between personality disorders/traits and addictions is a complex one and it has even been suggested that personality disorders/traits may come about as a result of the stresses of addictions such as poor quality of life and repeatedly needing to conceal the problem.

Particular patterns of personality disorders and subclinical maladaptive personality traits can form the internalizing and externalizing disorders, as discussed above, and these two domains can then, in turn, form pathways to different types of behaviours. Internalizing disorders are typically associated with behaviours such as addictions, self-harm and eating disorders and these behaviours are usually directed at the self. Externalizing disorders tend to be associated with disinhibited behaviours such as aggression, delinquency and addictions and these behaviours are typically aimed at others. The two disorder domains are both highly correlated with addictions but they each form a unique pathway and the addiction “types” differ in manifestation, aetiology and prognosis. The strong association of internalizing and externalizing disorders with addictive behaviours is supported by the findings of Chan and colleagues that 78-90% of adults and adolescents with substance use problems also had an internalizing or externalizing disorder and 42-61% had both.

The internalizing pathway to addictions typically involves emotion dysregulation which means that the individual is unable to effectively manage their emotions. The individual may begin using a substance or activity in order to alleviate psychological distress which is known as experiential avoidance. Emotion dysregulation in daily life could eventually bring about the heightened stress and anxiety of internalizing disorders which in turn could lead to addictions. Alternatively, these internalizing disorders may arise for other reasons and in turn poor emotion regulation abilities may then lead to addictions as an alternative method of regulating and coping. It has also been suggested that internalizing disorders may lead to addictions via rumination which is repetitively thinking about one’s distress and their negative situation without considering how to solve the problem. Adrian, McCarty, King, McCauley and Stoep's study supports the suggestion that the pathway from internalizing disorders to addictive behaviours may be mediated by rumination. The relationship between internalizing disorders and addictions is not simply a linear one as there are some studies which indicate that affective disorders sometimes follow addictions as opposed to precede them. There has also been research proposing that internalizing disorders do not contribute at all to the risk for addictions both in adolescents and adults.

Zucker’s review of the literature revealed that the externalizing pathway to addiction is underlined by the core construct of disinhibition which is the inability or failure to inhibit impulsive behaviour even when the negative consequences are known. McCormick and Smith found a significant association between aggression/hostility and substance use disorders which supports the theory of disinhibited behaviour as an important construct. The researchers also found that individuals with externalizing disorders typically used aggressive confrontational coping styles to deal with problems. Interestingly, some of those with externalizing disorders seemed to use avoidant coping styles, similar to those with internalizing disorders, and adopted disinhibited behaviours to avoid experiencing negative affect. Zucker and colleagues propose that there are essentially two main neural systems that make up disinhibition. Effortful Control involves controlling behaviour and attention in order to work towards a goal that is distal in time. Incentive Reactivity is an automatic and fast response to potential immediate reward or loss. The development of both of these neural systems can be seriously disrupted by exposure to negative early life experiences. Also, exploring the natural undisrupted development of these two systems demonstrates that the brain structures associated with Effortful Control do not mature fully until early adulthood whereas the structures associated with Incentive Reactivity are mature and active throughout childhood and adolescence. This may help to explain why adolescents tend to display higher levels of externalizing disorders i.e. why they are more disinhibited. Although there is research suggesting that childhood or adolescent externalizing disorders can lead to addictive behaviours later in life there is also research which argues that externalizing behaviours such as aggression may come about as a result of the effects of substances and alcohol.

To summarise, the literature supports the existence of the domains of the internalizing and externalizing disorders and the relationships between these domains and addictive behaviours, although not always causal relationships. These two pathways to addictions are unique and understanding them can have great implications for treatment planning and success. Comorbidity of addictions with mental health problems such as internalizing and externalizing disorders can lead to more severe forms of addictive behaviours in both adults and adolescents therefore, this clearly needs to be taken into account for treatment planning. Individuals with externalizing addictions had poorer treatment and behaviour outcomes and relapsed sooner and more frequently and only those with internalizing addictions experienced any significant treatment benefits. Although there has been research into how addictions can vary in aetiology, prognosis and manifestation depending on internalizing or externalizing disorders, further research is needed to investigate the particular types of addictive behaviours associated with each domain. Currently, there appears to be little to no literature on this topic.