Comorbidity of Anxiety and Depression in Children and Adolescents: An Integrative Review

Much evidence exists documenting the comorbidity of anxiety and affective disorders in youth. Furthermore, comorbidity appears to have serious implications both in terms of severity of impairment and course of disorder. Despite this, little is known about the meaning behind the high rate of co-occurrence of anxiety and depression in children and adolescents. Several conditions exist that may give rise to comorbidity. Specifically, two disorders may be comorbid when there is a high rate of symptom overlap between the disorders, when one underlying construct is split into two separate disorders, when the disorders share common risk or etiological factors, or because one disorder causes or increases the risk of developing the second disorder. The present paper examines each of these explanations as they relate to the comorbidity of anxiety and depression in youth.     

Obsessive-compulsive disorder: boundary issues

The boundaries between obsessive-compulsive disorder (OCD) and other neuropsychiatric disorders remain unresolved and may well differ from one disorder to another. Endophenotypes are heritable, quantitative traits hypothesized to more closely represent genetic risk for complex polygenic mental disorders than overt symptoms and behaviors. They may have a role in identifying how closely these disorders are associated with another and with other mental disorders with which they share major comorbidity. This review maps the nosological relationships of OCD to other neuropsychiatric disorders, using OCD as the prototype disorder and endophenotype markers, such as cognitive, imaging, and molecular data as well as results from demographic, comorbidity, family, and treatment studies. Despite high comorbidity rates, emerging evidence suggests substantial endophenotypic differences between OCD and anxiety disorders, depression, schizophrenia, and addictions, though comparative data is lacking and the picture is far from clear. On the other hand, strong relationships between OCD, Tourette syndrome, body dysmorphic disorder, hypochondriasis, grooming disorders, obsessive-compulsive personality disorder, and pediatric autoimmune neuropsychiatric disorders associated with streptococcus are likely. Studies designed to delineate the cause, consequences, and common factors are a challenging but essential goal for future research in this area.     

Test of Alternative Hypotheses Explaining the Comorbidity Between Attention-Deficit/Hyperactivity Disorder and Conduct Disorder

There is significant comorbidity between attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD). The conclusions of studies that examined the causes of comorbidity between ADHD and CD conflict, with some researchers finding support for the three independent disorders model and others finding support for the correlated risk factors model. We tested these models and eleven alternative hypotheses using the same analytical approach. The participants were 110 monozygotic twin pairs and 181 dizygotic twin pairs recruited from the Colorado Learning Disabilities Research Center Twin Study. The three independent disorders model did not fit the data, whereas the correlated risk factors model fit the data well. Several other comorbidity models fit the data as well as or better than the correlated risk factors model. The results suggest that correlated risk factors are a better explanation for the comorbidity between ADHD and CD than a third, independent ADHD+CD subtype.     

Sensory-motor deficits in children with developmental coordination disorder, attention deficit hyperactivity disorder and autistic disorder

Children who have been diagnosed with any one developmental disorder are very likely to meet diagnostic criteria for some other developmental disorder. Although comorbidity has long been acknowledged in childhood disorders, little is understood about the mechanisms that are responsible for the high level of comorbidity. In a series of studies, we have investigated the link between sensory-motor deficits and developmental disorders. Poor sensory-motor integration has long been implicated as a cause of motor problems in developmental disorders such as developmental coordination disorder (DCD), and our recent research has also investigated sensory-motor deficits in children with attention deficit hyperactivity disorder (ADHD) and autistic disorder. Based on a critical examination of relevant literature and some of our recent research findings, we argue that the importance of poor sensory-motor functioning in discriminating children with different disorders has been underestimated. Poor sensory-motor coordination appears to be linked to DCD, but not ADHD. Also, sensory-motor deficits in children with DCD and autistic disorder may provide insight into some of the social difficulties found in these groups of children. This research will increase our understanding of why children with one developmental disorder typically also have problems in other areas.     

Young adult follow-up of hyperactive children: self-reported psychiatric disorders,comorbidity, and the role of childhood conduct problems and teen CD

We report on the psychiatric disorders present at young adult follow-up (Mean age 20–21 years; 13 + year follow-up) and the comorbidity among them for a large sample of hyperactive (H; N = 147) and community control (CC; N = 71) children. The H group had a significantly higher risk for any nondrug psychiatric disorders than the CC group (59% vs. 36%). More of the H group met criteria for ADHD (5%); major depressive disorder (26%); and histrionic (12%), antisocial (21%), passive–aggressive (18%), and borderline personality disorders (14%) at follow-up than the CC group. Severity of childhood conduct problems contributed to the risk for passive–aggressive, borderline, and antisocial personality disorders. But it only affected risk for antisocial personality after controlling for severity of teen conduct disorder (CD), which also contributed to the risk for these same 3 disorders. Examination for comorbidity among these disorders indicated that presence of either borderline or antisocial personality disorder significantly increased the risk for major depression and the other significant personality disorders. More of the hyperactive group had received various forms of mental health treatment during and since leaving high school than the control group. Results suggest that hyperactive children are at significant risk for at least 1 nondrug disorder in young adulthood, principally major depression and several personality disorders, and that this risk is largely mediated by severity of CD at adolescence.     

Comorbidity In Post-Traumatic Stress Disorder An Analysis of Community and Clinical Studies1

Post-traumatic stress disorder (PTSD) is alleged to be associated with high rates of concurrent psychological disorders. This paper considers the available literature regarding comorbidity in PTSD and reviews in detail the findings to date. This critical evaluation includes studies of clinical samples, veterans community surveys, and population surveys. It also presents new data drawn from 50 PTSD cases assessed at the Boston PTSD Center using a comprehensive, multidimensional diagnostic procedure. The data firmly support the notion that PTSD, regardless of the nature of the trauma, is associated with high rates of other major psychological disorders including substance abuse, major depression, and personality disorders. Despite these findings the issue of cause and effect surrounding comorbidity remains open at this time. More research is needed to determine if exposure to extreme stressors in fact produces the broad spectrum of psychopathology suggested by individuals with PTSD or whether individuals with intrinsic vulnerability are more likely to develop PTSD when exposed to extreme stressors. Implications of the findings from this review are discussed with respect to concepts in diagnosis and comorbidity.     

Comorbidity of Anxiety and Conduct Problems in Children: Implications for Clinical Research and Practice

Given the relative lack of research on the comorbidity of anxiety disorders (ADs) and conduct problems (oppositional defiant disorder, conduct disorder) in youth, we examine this comorbidity from both basic and applied perspectives. First, we review the concept of comorbidity and provide a framework for understanding issues pertaining to comorbidity. Second, we examine the comorbidity of ADs and conduct problems in both epidemiological and clinical studies. Third, we explore the artifactual and substantive reasons for the comorbidity of these disorders. Finally, we discuss the implications of comorbidity for assessment and treatment and provide recommendations for future directions in clinical research and practice.     

Primary prevention of secondary disorders: A proposal and agenda

This paper calls for consideration of a new class of preventive interventions designed explicitly to prevent comorbidity of psychiatric disorders. Epidemiologic data show that successful interventions of this type could be extremely valuable, as up to half of lifetime psychiatric disorders and an even larger percent of chronic and seriously impairing disorders occur to people with a prior history of some other disorder. Furthermore, a review of etiologic hypotheses concerning the causes of comorbidity suggests that interventions aimed at primary prevention of secondary disorders might be feasible. However, more basic risk factor research is needed on the causes of comorbidity before we can make a clear assessment of feasibility and discover promising intervention targets. A number of methodological problems arise in carrying out this type of formative research. These problems are reviewed and suggestions are offered for solutions involving innovations in measurement, design, and data analysis.     

Comorbid ADHD: Implications for the Treatment of Anxiety Disorders in Children and Adolescents

Despite high comorbidity rates and potential clinical implications, the influence of co-occurring attention-deficit/hyperactivity disorder (ADHD) on outcomes of cognitive-behavioral treatment (CBT) for anxious youth remains poorly understood. In this qualitative review, the current literature on the influence of comorbid ADHD on CBT of youth with diverse anxiety disorders is explored. Peer-reviewed studies examining ADHD, at the diagnostic and symptom level, received highest priority. In addition, inasmuch as some studies did not isolate the effects of ADHD from other disruptive behavior disorders (DBDs: oppositional defiant disorder, conduct disorders), studies with the three DBDs were explored as well. Ten studies met our specified methodological criteria. Findings are discussed in relation to the following two factors: type of anxiety disorder and measurement of ADHD (diagnostic or symptom level) in these studies. There was evidence that youth with a variety of anxiety disorders and with co-occurring ADHD fared worse than their counterparts without ADHD. Additionally, grouping ADHD with other DBDs tended to obscure the negative impact of ADHD on treatment outcomes. Additional research is needed to delineate the influence of comorbid ADHD specifically on treatment outcomes for the various anxiety disorders. Clinical implications of treating anxious youth with comorbid ADHD are explored.     

Homeless Youths and Young Adults in Los Angeles: Prevalence of Mental Health Problems and the Relationship Between Mental Health and Substance Abuse Disorders

Although understanding of the subsistence patterns, service utilization, and HIV-risk behaviors of homeless youths and young adults is increasing, relatively little is known about the epidemiology of mental health problems in this group or the relationships between mental health problems and substance use. This study measured symptoms of depression, low self-esteem, ADHD, suicidality, self-injurious behavior (SIB), and drug and alcohol use disorder in a sample of homeless youth and young adults living in Hollywood, CA. Results indicated extremely high prevalences of mental health problems, as compared with corresponding rates of mental health problems found among housed youths in previous studies. Prevalence of mental health problems differed by age and ethnicity. African Americans were at lower risk of suicidal thoughts and SIB than were those of other ethnicities. Older respondents and females were at increased risk of depressive symptoms, and younger respondents were at increased risk of SIB. Previous history of sexual abuse and/or assault was associated with increased risk of suicidality and SIB. Risk factors for drug abuse disorder included ethnicity other than African American, homelessness for 1 year or more, suicidality, SIB, depressive symptoms, and low self-esteem. Risk factors for alcohol abuse disorder included male gender, white ethnicity, homelessness for 1 year or more, suicidality, and SIB. Extremely high rates of mental health problems and substance abuse disorders in this sample suggest the need for street-based and nontraditional mental health services targeted toward these youths and young adults.     

Psychiatric Comorbidity in Children with Autism Spectrum Disorders: A Comparison with Children with ADHD

The present study was conducted with the aim to identify comorbid psychiatric disorders in children with autism spectrum disorders (ASD) (n = 40) and to compare those comorbidity rates to those in children with attention deficit hyperactivity disorder (ADHD) (n = 40). Participants were clinically referred children aged 7–18 years. DSM-IV classifications were used for the primary diagnosis (ASD/ADHD), while comorbid psychiatric disorders were assessed using a structured diagnostic interview, the structured clinical interview for DSM-IV, childhood diagnoses (KID-SCID). Twenty-three children with ASD (57.5 %) had at least one comorbid disorder, whereas 16 children with ADHD (40.0 %) were classified as having at least one comorbid disorder. No group differences were found with respect to this comorbidity rate or for the rate of comorbid externalizing disorders (ODD and/or CD). However, children with ASD had more comorbid internalizing disorders compared to children with ADHD. More specifically, children with ASD had higher rates of anxiety disorders, but not mood disorders. No associations between comorbidity and age or between comorbidity and the intelligence quotient was found. It is important for clinicians to always be aware of, and screen for, comorbidity, and to consider treatment for these comorbid disorders. In addition, research should focus on establishing valid and reliable screening tools as well as effective treatment options for these comorbid disorders.     

Cognitive-affective neuroscience of somatization disorder and functional somatic syndromes: reconceptualizing the triad of depression-anxiety-somatic symptoms

Somatization disorder is a somatoform disorder that overlaps with a number of functional somatic syndromes and has high comorbidity with major depression and anxiety disorders. Proposals have been made for revising the category of somatoform disorders, for simplifying the criteria for somatization disorder, and for emphasizing the unitary nature of the functional somatic syndromes in future classifications. A review of the cognitive-affective neuroscience of somatization disorder and related conditions suggests that overlapping psychobiological mechanisms mediate depression, anxiety, and somatization symptoms. Particular genes and environments may contribute to determining whether symptoms are predominantly depressive, anxious, or somatic, and there are perhaps also overlaps and distinctions in the distal evolutionary mechanisms that produce these symptoms.     

The developmental mental-disorder histories of adults with posttraumatic stress disorder: a prospective longitudinal birth cohort study

Clinical and epidemiologic studies have established that posttraumatic stress disorder (PTSD) is highly comorbid with other mental disorders. However, such studies have largely relied on adults' retrospective reports to ascertain comorbidity. The authors examined the developmental mental health histories of adults with PTSD using data on mental disorders assessed across the first 3 decades of life among members of the longitudinal Dunedin Multidisciplinary Health and Development Study; 100% of those diagnosed with past-year PTSD and 93.5% of those with lifetime PTSD at age 26 had met criteria for another mental disorder between ages 11 and 21. Most other mental disorders had first onsets by age 15. Of new cases of PTSD arising between ages 26 and 32, 96% had a prior mental disorder and 77% had been diagnosed by age 15. These data suggest PTSD almost always develops in the context of other mental disorders. Research on the etiology of PTSD may benefit from taking lifetime developmental patterns of comorbidity into consideration. Juvenile mental-disorder histories may help indicate which individuals are most likely to develop PTSD in populations at high risk of trauma exposure.     

Current and lifetime comorbidity of the DSM-IV anxiety and mood disorders in a large clinical sample.

The comorbidity of current and lifetime DSM-IV anxiety and mood disorders was examined in 1,127 outpatients who were assessed with the Anxiety Disorders Interview Schedule for DSM-IV: Lifetime version (ADIS-IV-L). The current and lifetime prevalence of additional Axis I disorders in principal anxiety and mood disorders was found to be 57% and 81%, respectively. The principal diagnostic categories associated with the highest comorbidity rates were mood disorders, posttraumatic stress disorder (PTSD), and generalized anxiety disorder (GAD). A high rate of lifetime comorbidity was found between the anxiety and mood disorders; the lifetime association with mood disorders was particularly strong for PTSD, GAD, obsessive-compulsive disorder, and social phobia. The findings are discussed in regard to their implications for the classification of emotional disorders.     

Aetiology of Coexisting Mental Health and Alcohol and Other Drug Disorders: Perspectives of Refugee Youth and Service Providers

In the general population, people with comorbid mental health (MH) and alcohol and other drug (AOD) disorders (comorbidity) have great difficulty accessing appropriate services, and poor outcomes. Little is known about comorbidity in resettled refugees in Australia. This study was designed to identify risk factors and patterns of comorbidity development in young people from refugee backgrounds living in a disadvantaged urban region of Adelaide, South Australia. This qualitative study utilised in‐depth semi‐structured interviews (n = 30) with resettled refugee youth and workers from MH, AOD, and refugee support services. Thematic analyses were conducted to investigate the aetiology of MH and AOD disorders in young refugees. Interviews with both groups revealed how the interrelated nature of risk factors may place young people from refugee backgrounds at heightened risk of experiencing MH and AOD problems. The situations and conditions described by both groups are discussed under six main themes: pre‐migration experiences of torture and trauma; familial factors of intergenerational conflict; post‐migration adjustment difficulties in terms of language, culture, education, and employment; exposure to and availability of substances; maladaptive coping strategies and self‐medication; and access to information and services. Implications for psychologists and MH professionals are identified, emphasising the need for clinicians to understand the complexities surrounding the aetiology of comorbidity in these youth. The initial assessment needs to be comprehensive, including pre‐ and post‐settlement experiences and cultural and family dimensions of their current situation. Treatment may often need to simultaneously address multiple contributing factors and involve culturally sensitive psycho‐education.     

Why does ADHD Confer Risk for Cigarette Smoking? A Review of Psychosocial Mechanisms

Research has documented that adolescents and young adults with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for cigarette smoking, but less attention has examined why this risk exists. The current paper reviews the literature on different psychosocial mechanisms [self-medication hypothesis, social factors (social modeling, social impairments), cognitive factors (attitudes, coping skills), and psychological variables (ADHD symptom dimensions, comorbidity)] that might explain this increased smoking risk. Results of the review suggest that, while the self-medication hypothesis has some theoretical merit, it has not been adequately examined among adolescents and young adults with ADHD. Further, cognitive and social factors may be important mechanisms that help to explain the association between ADHD and cigarette smoking, but research in these areas is sparse. Finally, a larger body of literature suggests that different psychological aspects of ADHD (e.g., comorbidity, symptom dimensions) are related to smoking. Interpretation of findings of many of these studies was hindered due to significant methodological problems and the lack of a guiding theoretical orientation. Potential theories that might facilitate future work in this area are discussed. Future research should continue to explore these important psychosocial mechanisms as well as gene–environment interactions in examining the link between ADHD and cigarette smoking.     

Children of Mentally Ill Parents Participating in Preventive Support Groups: Parental Diagnoses and Child Risk

In the Netherlands, preventive support groups are offered to children of mentally ill parents. Given the variety of parental diagnoses it might be questionable if offering a standardized program for all these children is the most effective response. While no overall knowledge exists about the type of parental disorder and varying risk levels and support needs among the participating children, we examined whether there are differences between these children that are related to their parents’ diagnoses. With questionnaires we assessed risk factors in 122 mentally ill parents and their children: high parental illness severity, low perceived parental competence, parent–child interaction problems, poor family functioning, difficult child temperament, and low child competence. We also assessed the children’s psychosocial problems and negative cognitions about their parent’s illness. Results showed that most parents had co-morbidity (multiple diagnoses) and/or personality disorders. Children of parents with either of these conditions were more likely to be exposed to the risk factors: high parental illness severity, low perceived parental competence, problematic parent–child interaction, and low perceived child competence, compared to children of parents without these conditions. They were also faced with more risk factors and had more psychosocial problems and negative cognitions. From these results we may conclude that children of parents with co-morbidity and/or personality disorders require more extensive support than children of parents without these conditions. We suggest strengthening the children’s competence and involving parents as important focuses of preventive interventions for children at high risk. Longitudinal studies should test these assumptions.     

Cognitive processing of body and appearance words as a function of thin-ideal internalization and schematic activation

To better understand how women at risk of body image disturbance respond when their body concerns are activated, we examined attentional and memory biases in undergraduate women with high thin-ideal internalization, an identified risk factor for eating disorders, following priming of body and appearance concerns. Female undergraduates (N = 186) viewed photos of either sports cars or attractive swimsuit models, then completed the Lexical Decision Test, a word recall test, and questionnaires assessing thin-ideal internalization and eating disorder symptomatology. High thin-ideal internalizers did not exhibit cognitive biases predicted by cognitive models of eating disorders, even when their body and appearance concerns were primed by exposure to attractive models. Converging evidence suggests that high-risk non-clinical samples rarely exhibit cognitive biases characteristic of individuals with eating disorders, and, in fact, may actually incorporate ideal appearance into their schemas and preferentially attend to attractive stimuli.     

Nature, Nurture, and Attention Deficit Hyperactivity Disorder

This commentary shows that Joseph's (this issue) review of the genetics of attention deficit hyperactivity disorder (ADHD) contains errors of scientific logic and ignores much relevant research. Thus, we reject his conclusions. We also reject Joseph's approach of pitting nature against nurture as if these two facets of human life are at odds with one another. Instead, most scientists who study the genetics of psychiatric disorders embrace the idea that these disorders are influenced by both genes and environmental factors. In fact, the twin studies criticized by Joseph provide the strongest evidence that environmental risk factors play a substantial role in the etiology of ADHD. They do so by showing that when one identical twin has ADHD the risk to the co-twin is much less than 100%, a fact which can only be explained by environmental risk factors. We also reject the idea that genetic studies have hindered psychosocial research, stigmatized patients, or promoted psychopharmacologic treatments. Genetic studies have aimed at solving one part of the puzzle of ADHD. By testing a parsimonious theory, they have set the stage for gene discovery and the delineation of how genes and environment combine to cause this impairing disorder.     

Dependency,impulsivity, and self-harm: traits hypothesized to underlie the association between cluster B personality and substance use disorders

Cluster B personality disorders (PDs) (i.e., antisocial, borderline, histrionic, and narcissistic) typically show a high degree of comorbidity with substance use disorders (SUDs). Previous research suggests that the broad-based personality domains of Disinhibition and Negative Temperament/Neuroticism may be common factors to both types of disorders. Using a two-phase process (i.e., screening and follow-up), this study examined three lower-order personality traits (i.e., dependency, impulsivity, and self-harm) that fall within the Disinhibition and Neuroticism domains. The study evaluated the hypotheses that these traits (a) are related both to cluster B PDs and to SUDs; and (b) underlie the association between the two types of disorders. Results indicate that impulsivity and self-harm play a significant role in cluster B PDs and SUDs, as well as in their association with each other. However, dependency was not associated with either type of disorder. These results indicate that sets of individual traits can be of significant utility in understanding the comorbidity between PDs and SUDs.