CHAPTER 11: Depression and Infectious Diseases

INTRODUCTION

Depression and infectious diseases are linked in multiple ways. Depression contributes to initial infection in several diseases; for example depression predisposes to both hepatitis C (HCV) and HIV acquisition. Conversely, depression may result from the stress of living with a serious infectious disease, or may stem from the effect of an infectious disease on the immune and central nervous systems (CNS). In addition, the medications used to treat infectious diseases may cause depression. The interrelationship is further complicated by the fact that depression may be more prevalent among groups at greater risk of infection, such as individuals with substance-related conditions or individuals who are homeless or living in poverty.

Early identification and treatment of depression leads to improved quality of life and may improve medical outcomes by facilitating engagement in and adherence to the medical regimen. Given shared underlying pathophysiologic mechanisms, effective treatment of depression may in some instances even influence the course of disease. This chapter will address the salient features of depression found among those infectious diseases most commonly associated with mood disturbances.

HEPATITIS C

EPIDEMIOLOGY (FIG. 11-1)

PREVALENCE AND INCIDENCE OF DEPRESSIVE DISORDERS

Patients with HCV are disproportionately affected by depression, the most common mental health concern among HCV-infected individuals.^1–4 Compared to the general population, depression is three to four times more prevalent in individuals with HCV.^5–7 Current prevalence rates for depressive disorders among individuals with HCV range from 28% to 35%,^3,7–9 and lifetime rates are reported to be between 34% and 44%.^3,7 The prevalence of particular depressive disorders varies widely depending on the study; the prevalence of major depressive disorder (MDD) is variously reported between 8% and 25%.^3,7,10 The most common depressive diagnosis is adjustment disorder with depressed mood, reported in 40% of cases, while the least prevalent is dysthymia or depressive disorder NOS (3%).³

One alarming result of MDD is suicidal ideation and suicide attempts. HCV patients are twice as likely to have attempted suicide as matched controls.¹¹ The suicide risk is greater for males and those under 45 years of age.¹²

RISK FACTORS AND CORRELATES OF DEPRESSION

Increasing age is associated with greater risk for depression and severity of depression in those with HCV (Box 11-1).^3,13 As in the general population, the prevalence is higher in women (44%) with HCV than in men (22%).³