Social interactions at the level of support, cognition and attachment may contribute to emotional regulation and, if disturbed or absent, to the development of mental disorders. In addition to human Depression & Anxiety disorders [1], several studies have been published emphasizing social components in Posttraumatic Stress Disorder (PTSD) [2]. In particular, social support-like phenomena have drawn most attention presuming that support helps buffering against psychological distress. Meta-analyses examining risk factors of PTSD found that either the lack of social support or actively perceiving support both before and after a traumatic event are among the strongest predictors of PTSD diagnosis or symptoms [3,4]. Additionally, an inverse relationship between enhanced social support and suicidal behaviour has been observed in PTSD populations [5,6]. However, the processes underlying the effects of social context and support on development and maintenance of the disorder have only been sparsely investigated [7].
 
Apart from human studies, substantial knowledge on the neurobiology of social behavior has been gathered in experiments using laboratory animals. Rats and mice are thought to be social animals. Hence, prolonged isolation of animals, for instance by individual housing, is frequently considered as a model of chronic stress as it induces abnormalities in behavior and neurochemistry leading to the theory of the “isolation syndrome” in mice [8]. Reports on social isolation in rodents provide evidence for, e.g., increased anxiety-related behavior [9], anhedonia-like symptoms [10], increases in alcohol intake [11] and aggression [12]. In addition, the social environment also exerts physiological consequences. For instance, solitary housing induces reduced corticolimbic allopregnanolone levels [13], a down-regulation of serotonergic neurotransmission [14] and impaired hippocampal neurogenesis [15]. On the other hand, these findings strongly suggest a beneficial outcome of group or colony housing on animal behavior. Hence, social housing might favour alleviated emotional responses in potentially aversive situations by empathy-like phenomena among rodents [16-18].
 
In recent years, we have established a mouse model of PTSD [19,20] incorporating major criteria of the disease, i.e., symptoms of re-experiencing, hyper vigilance, avoidance and emotional numbing [21,22]. A major psychobiological concept of PTSD assumes that both fear conditioning and sensitization processes contribute to the development and maintenance of the disorder [23]. Mice receiving a single, inescapable electric foot shock develop strong traumaassociated contextual fear as well as non-associative, stress-related fear (i.e., freezing to a neutral tone) [24], hyper arousal [25] and avoidance behavior [26]. Intriguingly, these two components become manifest with the passage of time and seem to represent independent behavioral dimensions [24,25,27,28].
 
Regarding social factors, we could demonstrate the importance of the early postnatal social context in terms of maternal experience on the susceptibility to develop PTSD- like symptoms in mice [27]. Yet, there seems to be also a significant genetic component of individual susceptibility since the strain-dependent expression levels of PTSD-like symptoms persisted inter-strain embryo transfers [29]. In adulthood, enriched housing decreased the intensity of trauma-associated contextual fear and compensated for trauma-related volume loss of the hippocampus in our PTSD mouse model [30].

Citation: Thoeringer CK, Wotjak CT (2013) Evaluating Social Support-Like Phenomena in an Animal Model of Posttraumatic Stress Disorder (PTSD) J Depress Anxiety 3: 143. doi: 10.4172/2167-1044.1000143

 

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