So this is a two-part question. First we will answer the question, when does anxiety become a disorder? Anxiety disorders are diagnosed by psychiatrists utilizing the Diagnostic and Statistical Manual of Mental Disorders, with DSM-5 as the latest version (American Psychiatric Association [APA], 2013). Anxiety disorders are clinical diagnoses, meaning they are diagnosed based on clinical history and patient interview. Psychiatry currently has no biological tests to confirm the diagnosis of an anxiety disorder. So with a clinical diagnosis of an anxiety disorder, multiple factors are analyzed to determine if a person has an anxiety disorder, which includes the following: number of symptoms, difficulty controlling the anxiety, duration, frequency, intensity and impact on daily living. Each of the anxiety disorders has a list of symptoms, and each has a threshold number to meet the criteria for the diagnosis. So if one has the minimum threshold number of symptoms, then an anxiety disorder is likely. In generalized anxiety disorder, in addition to worry and anxiety, one needs 3 or more additional symptoms in order to meet threshold criteria for disorder. However, it is not enough to just meet the threshold criteria to have a disorder. One need to have difficulty controlling the anxiety, and one also needs to meet a duration criteria. In generalized anxiety disorder, the anxiety and worry needs to occur for at least 6 months to be a disorder. Still, meeting the criteria for number of symptoms and duration, and having difficulty controlling the anxiety is not enough. The symptoms also need to be present for most of the time, meaning most of the day and most days of the week are filled with the anxiety symptoms. In addition, for an anxiety diagnosis, the intensity of the symptoms is so severe that it disrupts job performance, relationships, and/or other areas of functioning. So the intensity, frequency and/or duration of the anxiety and worry are out of proportion to the impact of the feared situation.
And after all this, it still may not be an anxiety disorder, as other factors need to be considered. It is important to rule out medical causes of anxiety, such as thyroid problems, and if a general medical condition is present, to treat the underlying medical problem. Also, it is important to rule out substance abuse causing the anxiety, and that treatment for substance abuse may need to be initiated. Psychiatrists also factor in other variables when formulating an anxiety diagnosis. Other factors include the cultural context of the anxiety and worry, as the anxiety may be normal in one`s particular culture, while it may be excessive in another culture. Psychiatrists also factor in the family history, as anxiety disorders tend to run in families, and hypothesized to have both genetic and environmental (ie modeling of behaviour from parents) influences. In addition, psychiatrists factor in the age of onset and course of the illness, as particular anxiety disorders have their own patterns with regards to onset and course. And then the psychiatrist factors in the psychology of the patient and the social environment of the patient, which also impacts the anxiety and the possible manifestation of an anxiety disorder. So as you see, the process of diagnosing an anxiety disorder from a psychiatrist is not merely an exercise in checking off checklists. Psychiatric diagnosis of an anxiety disorder is a complex and analytical process, as described above.
The second part of the question is: how does anxiety become a disorder? The answer to this is unknown, given that not only do we not have a biological test to diagnose an anxiety disorder, but we really do not know how anxiety becomes a disorder. While the neurobiology of anxiety disorders is advancing, it is not developed to the point where we can take an MRI of the brain or take a blood sample to determine if one indeed has an anxiety disorder. The fact that we don’t have a biological marker to diagnose anxiety is a travesty, considering all the research and research dollars and dozens of psychiatry journals dedicated to studying the neurobiology of anxiety disorders. Patients deserve more, and frankly, psychiatry is not accommodating their needs, in the face of all these resources and technology to look at the underpinnings of anxiety disorders. The best that modern psychiatry, in 2014, can do is come up with the DSM-5 (APA, 2013), which is not an improvement to DSM-IV (APA, 2000), as DSM-5 still does not give us biological markers for diagnosing psychiatric illness.
So back to the question, how does anxiety become a disorder? The best way to answer this question is to look at a comprehensive model for formulating mental illness, the biopsychosocial model (Engel, 1977; Carandang, 2009). When utilizing the biopsychosocial model, one can hypothesize how one may develop an anxiety disorder, and how one may be at risk for developing one. In the biopsychosocial model, there are 4 factors to consider across the domains of the model: 1) predisposing factors, 2) precipitating factors, 3) perpetuating factors, and 4) protective factors. So with regards to risk for an anxiety disorder, a predisposing factor such as family history of an anxiety disorder places one at risk for also developing an anxiety disorder. A precipitating factor that may trigger the development of an anxiety disorder may be stressors such as substance abuse, trauma, loss, financial problems, and relationship problems, just to name a few. And then there are perpetuating factors which help to maintain the anxiety disorder, such as inadequate treatment, basic needs not met, housing instability, etc. Finally, there are protective factors, which is the only factor which counteracts the development of an anxiety disorder. For instance, when one has good adaptive coping skills, or has excellent support from their family, or has adequate exercise and good sleep, these are considered protective factors. So that the more protective factors one has, then this can help to either prevent the development of an anxiety disorder, or can help to treat the active disorder and recover.
In summary, when anxiety becomes a disorder is based on a complex and analytic process that is the art of psychiatric diagnosis. Unfortunately, biological markers for anxiety disorders are not present at this time, and the field needs to move forward and incorporate objective tests to confirm the diagnoses of anxiety disorders. Until we have such biological markers, then we will not have a complete understanding of how anxiety becomes a disorder.