SPOILER ALERT!
~ Smoking worsens anxiety and prolong its course
~ Smoking appears to reduce some of the symptoms of anxiety
~ There are more smokers among PD disorders than among OCD disorders.
~ Nicotine affects the fear response.
Smoking in anxiety disorders has paradoxical effects. Indeed, there is evidence that nicotine dependence contributes to the worsening of anxiety symptoms, but studies also suggest that smoking helps alleviate symptoms of anxiety such as hyperarousal, emotional numbing, and avoidance.
Interestingly, we see heterogeneity in smoking behaviors across all anxiety disorders. For example, panic disorder has the highest prevalence of smoking, which incidentally contributes to the initiation and maintenance of panic attacks, while OCD presents the lowest rates of smoking. One likely explanation for these differences could be found in how nicotine affects the different neural pathways (i.e., the brain circuits activated in anxiety) underpinning the various subtypes of anxiety disorders.
All anxiety disorders are not created equal
The central hypothesis for the neurobiology of anxiety disorders highlights a shift in the control of behavior from the cognitive (i.e., rational thinking, judgment, etc…) to the emotional following a traumatic event or a stressful period. More specifically, we see a disruption in the balance between prefrontal (i.e., brain regions involved in thinking, decision-making, concentration) and limbic regions (i.e., involved in emotion processing), including the amygdala – essential in the fear learning process- and the hippocampus which is a structure that plays a crucial role in memory formation and consolidation.
For example, post-traumatic stress disorder (PTSD) is characterized by an increased activity in both the amygdala and the hippocampus, which contributes to the PTSD symptoms. In panic disorder, we also see abnormalities with the hippocampus, while generalized anxiety disorder (GAD) exhibits hyperactive amygdala. Taken together, these results implicate a functional disruption within the brain structures involved in the fear response and fear memory in anxiety disorders.
The link between nicotine and fear
Nicotine, however, has been found to modify the fear response (i.e, fear-learning and fear extinction) to a varying degree depending on its administration (i.e., acute, chronic or withdrawal), which suggests that nicotine influences the hippocampus. For example, animal studies suggest that acute nicotine intake amplifies fear memories and possibly worsens fear-related symptoms in anxiety disorders such as intrusive memories.
In addition, while chronic nicotine had no effect on fear memory, withdrawal from chronic nicotine was associated with psychological symptoms such as irritability, restlessness, insomnia, poor concentration, and depression, thus making it harder to quit smoking Furthermore, it is suggested that the effects of nicotine could lead to reduced effectiveness of exposure therapy (where the goal is to confront one’s learned fear/phobia) and prolong the course of the anxiety disorder.
Reference:
Kutlu, M. G., & Gould, T. J. (2015). Nicotine modulation of fear memories and anxiety: Implications for learning and anxiety disorders. Biochemical pharmacology, 97(4), 498–511. https://doi.org/10.1016/j.bcp.2015.07.029