Psychobiological Aspects of Asthma and the Consequent Research Implications: THE INTERACTION OF MEDICAL part 2
A further biologic factor that may cause anxiety may occur if hyperventilation and panic are misconstrued as being indicative of a worsening of the patients respiratory disorder. If this happens, then dosages of asthma medications may be inappropriately increased which in the case of methylxanthines and p2-adrener- gic agonists are likely to make patients physiologically even more agitated and anxious.
Other evidence suggesting a biologic component to the anxiety disorders seen in asthmatics is the finding, which confirms the genetic predisposition of patients with anxiety disorders, of an increased rate of past personal and family psychiatric histories in asthmatic patients diagnosed as psychiatrically ill compared with psychiatrically fit asthmatics.
A final indicator toward a biologic component to the anxiety disorders is the as yet unreported clinical observation that we have made that tricyclic antidepressants not only improve mood disorders of asthmatic patients but in certain cases have also markedly improved their functional asthma status. This is strong clinical evidence in support of the widely held lay view that there is an important central nervous system component in asthma and is supported by the few studies in the literature using tricyclic antidepressants in asthmatics. Goldfarb and Venutolo used 25 mg of imipramine in an uncontrolled trial in patients who were described as having chronic allergic asthma. They concluded that imipramine was a “useful and safe drug in the treatment of chronically ill depressed allergic patients.” Sugihara et al, in another nonblind uncontrolled study, concluded that amitriptyline (in doses varying from 20 to 120 mg) was helpful in the treatment of patients either in status asthmaticus or who suffered recurrent attacks of asthma, while Meares et al also noted that amitriptyline could ameliorate symptoms of asthma. The whole question of the effect of the psychotropic drugs on respiration has been extensively surveyed by Steen and by Dudley and Sitzman. These authors have concluded that in general, tricyclic antidepressants are safe, with little or no effect on the respiratory center, as long as prescribed appropriately. Dudley and Sitzman suggested that doxepin, a tricyclic antidepressant, might actually have a bronchodilator effect.
At a biologic level there are, therefore, a variety of factors that suggest that asthmatic patients are more likely to develop biologically based anxiety disorders than would normally be expected. Clearly, patients who are genetically vulnerable to anxiety disorders are most at risk as they would be expected to have an underlying cerebral anatomic and/or physiologic abnormality, and to be more susceptible to the effects of dyspnea, hyperventilation, and the centrally stimulant medications prescribed for the treatment of asthma. The biologic overlap between asthma and anxiety disorders merits considerable further research.
The psychosocial issues facing patients with asthma may combine with these biologic factors to further increase the likelihood of the development of anxiety disorders in these patients.