As outlined in the Preface, there are compelling reasons for all clinicians to become familiar with mental and addiction disorders: they provide the vast majority of all care!

To provide effective guidelines for clinicians, we need a different approach to teaching about mental disorders than has typically been used. We define mental disorders as both mental and substance use disorders.¹ Psychiatry textbooks typically focus on psychological symptoms, such as feeling sad or worried, to make a mental disorder diagnosis, for example for depression or panic disorder. In medical settings, however, a far more complex job emerges. You must address physical as well as psychological symptoms. While you are already familiar with physical symptoms related to diseases, their role in mental health disorders is less often considered.

To guide you, Chapters 1 and 2 are devoted to the key role physical symptoms play in mental health diagnoses in medical settings. In this chapter, we begin by presenting 3 axioms for mental health care. They will help you identify the group of patients in whom you most likely will find mental disorders.

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  Axiom 1: Mental and medical disorders often coexist. Such co-occurrence of disorders is called comorbidity; one disorder is comorbid with the other. Successfully addressing one requires effectively addressing both disorders.^2,3

  
  
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  Axiom 2: Many mental health disorders present with chronic and disabling physical symptoms. Patients with mental health disorders in medical settings often do not present with psychological symptoms. Rather, physical symptoms typically predominate and can obscure the psychological symptoms of the mental disorder. There are no specific physical symptoms associated with mental disorders, and they may involve any body system. However, there is 1 unique feature: the more severe, chronic, and disabling the physical symptoms, the more likely there is an associated mental disorder.⁴ While psychological symptoms are always essential in diagnosing mental disorders, they are not a sufficient initial presenting symptom to rely on for identifying many mental and substance use disorders. Often, the psychological symptoms (and the mental disorders they represent) become apparent only when providers with an index of suspicion inquire directly about them.⁴

  
  
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  Axiom 3: There are 2 common types of chronic physical symptom presentations of a mental disorder: medical disease and medically unexplained symptoms (MUS).

  
  
  
  
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    Many mental disorders pair with a chronic medical disease, at least in part because of its adverse psychological impact; for example, the dyspnea of severe heart failure may produce depression because the patient can no longer play golf, do housework, go to church, or rake the yard. In this situation, the severe physical symptoms and disability of a chronic medical disease can be considered a “red flag” for an associated mental disorder.

    
    
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    Many mental disorders present with chronic MUS, defined as physical symptoms that have little or no identifiable disease or pathophysiologic basis.^5,6 Chronic unexplained physical symptoms, such as severe chronic pain or disabling chronic fatigue, also are closely associated with mental disorders, such as depression or anxiety, and are another “red flag” indicating an associated mental disorder.

Why don’t patients immediately express psychological symptoms in addition to their physical symptoms? The stigma of having a mental disorder is a common explanation.^7-9 Additionally, patients may think that medical clinicians are not interested in their psychological symptoms or they simply may not be accustomed to discussing their psychological symptoms in medical settings. Also, they may not be fully aware of their psychological symptoms. In all patients presenting with chronic physical symptoms, therefore, careful inquiry about associated psychological symptoms usually must occur to identify the mental health disorder.

Now let’s examine these axioms in greater detail.

Comorbidity, the co-occurrence of 2 or more diagnoses, is the rule in medicine whether involving mental disorders, medical disorders, or both,¹⁰ for example depression and cancer, depression and anxiety, or diabetes and angina pectoris. Although current medical practices often focus on just the disease, it has been well demonstrated that treating the comorbid mental health problem improves the medical problem beyond the impact of medical treatment alone.^11-13 For example, treating comorbid depression in patients with diabetes improves control beyond just treating the diabetes because, for example, as they become less depressed, patients are better able to control their medications and diet.¹⁴

Medical clinicians encounter many comorbid mental disorders. Prevalence data indicate the following: (1) 25% of clinic patients will have a major mental disorder¹⁵ and 68% of these will have a comorbid disease of some type; and (2) 58% of clinic patients will have a disease, 29% of whom have a comorbid mental disorder.¹⁶ The more severe and chronic the medical disease, the more likely there is an associated mental disorder.¹⁷

Rarely do the mental disorder and the associated disease act independently. Rather, they almost always interact. Consider the following examples:

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   Chronic disease leads to a mental disorder; for example, immobility and inability to work due to cancer or angina pectoris leads to new or worsening depression.

   
   
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   Mental disorder leads to a chronic disease; for example, alcoholism leads to cirrhosis of the liver, and depression leads to poor adherence to diabetes treatment and, in turn, poor control.

   
   
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   Disease treatment leads to a mental disorder; for example, corticosteroid or thyroid medications lead to anxiety, and β-blockers lead to depression. (See Table 1-1.)

   
   
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   Mental disorder treatment leads to a chronic disease; for example, an antidepressant or atypical antipsychotic increases the QT interval in a patient with heart disease. (See Table 1-2.)

   
   
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   Disease itself directly causes a mental disorder, for example depression from hypothyroidism, Cushing’s disease, or hyperparathyroidism, and anxiety from a pheochromocytoma. (See Table 1-3.)