Huntington’s disease is an autosomal-dominant neurodegenerative disease that is characterized by a triad of symptoms, including cognitive disturbance, motor abnormalities, and psychiatric features. The disease results from a trinucleotide CAG expansion on chromosome 4. The prevalence of Huntington’s disease is approximately 7–10 per 100,000 individuals (1, 2). Disease onset typically occurs between the ages of 35 and 44 years, with an average survival of 20 years. There is currently no cure for the disease, although treatments to slow the progression of symptoms are currently being developed.

It is well established that psychiatric symptoms are common in Huntington’s disease (3–5). In fact, completed suicide has been reported to be as high as 13% in Huntington’s disease (3), reflecting a seven- to 12-fold increase from the rate in the general population (6, 7). Comparison with other research suggests that suicide rates in Huntington’s disease remain higher than those found in other medical and neurodegenerative diseases (8, 9).

Although it is considered mandatory to inquire about suicidal ideation in psychiatric consultations, it is seldom part of the traditional medical or neurological assessment. Most research on suicide risk in Huntington’s disease has focused on persons undergoing genetic testing (7, 10, 11). Less attention has been devoted to suicidal ideation over the stages of presymptomatic and diagnosed Huntington’s disease. In developing suicide prevention practice guidelines for Huntington’s disease, it is imperative to know what factors may involve an increased suicide risk and, if possible, when in the course of the disease the risk is greatest. In the studies published to date, controversy exists about whether suicide risk is elevated in the earliest (12) or the later stages of Huntington’s disease (7).

The purpose of the present study was to examine suicidal ideation in individuals at risk for and diagnosed with Huntington’s disease. A large number of participants from the Huntington Study Group were evaluated with the Unified Huntington’s Disease Rating Scale (13) and grouped according to ratings obtained from its standardized neurological examination and total functional capacity rating scales. The proportion of persons in each group who endorsed suicidal ideation was compared among groups. The informed consent from the Unified Huntington’s Disease Rating Scale was approved by each institution’s ethics review board.

Procedure

The participants were evaluated with the Unified Huntington’s Disease Rating Scale (13) by Huntington Study Group members from 43 sites in North America, Australia, and Europe. All participants were grouped according to a standardized neurological examination administered by an experienced movement disorder neurologist. The diagnosis of Huntington’s disease was based upon the findings obtained from the motor section of the Unified Huntington’s Disease Rating Scale, and diagnostic confidence was reported based upon the following scale: 0=normal neurological examination, 1=nonspecific motor abnormalities or soft signs, 2=motor abnormalities that indicated possible Huntington’s disease, and 3=unequivocal motor abnormalities that indicated definite Huntington’s disease. Good reliability has been demonstrated for the diagnosis of Huntington’s disease with the Unified Huntington’s Disease Rating Scale (14). Since the participant group with a definite diagnosis of Huntington’s disease was large (i.e., 2,688 individuals) and Huntington’s disease is often characterized by stage of illness, this group was further grouped by stage of disease (stages 1 to 5) with a measure of total functional capacity (15) from the Unified Huntington’s Disease Rating Scale. The percentages of individuals in each group who acknowledged suicidal ideation upon questioning were compared.

Participants

The total study group consisted of 4,171 individuals. There were 1,483 persons not diagnosed with Huntington’s disease but considered "at risk" for the disease by virtue of having a parent with Huntington’s disease. Of these, 712 were classified as having no motor symptoms of Huntington’s disease (i.e., a score of 0 for motor evaluation on the Unified Huntington’s Disease Rating Scale). Three hundred sixty-three people showed minor soft signs (score of 1), and 408 showed motor symptoms that indicated possible Huntington’s disease (score of 2). Two thousand, six hundred eighty-eight people received a score of 3 on the motor evaluation, indicating that they had been diagnosed with definite Huntington’s disease. Of these individuals, 2,637 (98%) also had complete data regarding stage of Huntington’s disease based upon functional capacity scores (15). Six hundred eleven (23%) of these individuals were in stage 1, 923 (34%) were in stage 2, 724 (27%) were in stage 3, 277 (10%) were in stage 4, and 102 (4%) were in the final stage (stage 5) of the disease.

Demographic characteristics for the participant groups are presented in t1. Briefly, the participants’ ages ranged from 20 to 90, with an average age of 47 years (SD=13). Not surprisingly, increasing age was associated with greater deficits on the neurological examination. As shown in t1, the participants with definite Huntington’s disease were, on average, older than the at-risk participants. The average level of education of the study group was approximately 13 years (SD=3). In general, the study group was more than 90% Caucasian, approximately 46% were men, and the majority of the participants were right-handed.

Measures and Group Division

The Unified Huntington’s Disease Rating Scale is a standardized clinical rating scale that assesses four components of Huntington’s disease: motor function, functional capacity, cognitive ability, and psychiatric symptoms. The motor section of the Unified Huntington’s Disease Rating Scale assesses motor features of Huntington’s disease with standardized ratings of oculomotor function, dysarthria, chorea, dystonia, gait, and postural stability.

The Unified Huntington’s Disease Rating Scale’s functional assessment consists of the Huntington’s disease functional capacity scale, the independence scale, and the functional checklist (15). Higher scores on the functional capacity scales are indicative of better functioning.

The cognitive section of the Unified Huntington’s Disease Rating Scale includes the letter fluency test (16), the Symbol Digit Modalities Test (17), and the Stroop Color and Word Test (18). Higher scores on these measures are indicative of better performance.

The behavioral section of the Unified Huntington’s Disease Rating Scale includes standardized interview questions regarding the frequency and severity of psychiatric symptoms (i.e., depressed mood, low self-esteem, anxiety, suicidal thoughts, disruptive or aggressive behavior, irritable behavior, perseverative/obsessional thinking, compulsive behavior, delusions, hallucinations, and apathy). During the administration of the Unified Huntington’s Disease Rating Scale, the frequency of a behavioral symptom is initially rated; if the symptom is present, a rating of the severity of the symptom is made. In the current study, endorsement of suicidal ideation (presence or absence) was used to compare the proportion of each subgroup with suicidal thoughts. Next, the severity of suicidal thoughts (a rating of 1–4) was used to quantify the severity of suicidal thoughts in the persons endorsing these. Other Unified Huntington’s Disease Rating Scale measures used included diagnosis based upon the motor section of the Unified Huntington’s Disease Rating Scale and total score on the Huntington’s disease functional capacity scale.

Data Analysis

Study sites sent the Unified Huntington’s Disease Rating Scale forms to the coordination center at the University of Rochester, where data were entered. Data were cleaned and summarized at the University of Iowa. The percentage of participants with suicidal ideation endorsed was calculated within each group. The percentage of individuals experiencing suicidal thoughts was compared across groups. A chi-square test of independence was initially carried out to determine whether differences in the percentage of individuals with suicidal ideation across groups were large enough to warrant further comparisons. Significant findings were followed up with post hoc chi-square tests of independence between groups. After we compared the proportion of participants endorsing suicidal ideation, summed scores for suicidal severity were compared across groups.

The frequency distribution of suicidal ideation for the entire study group is presented in t2. Briefly, 82.5% did not endorse any suicidal thoughts. Mild suicidal ideation (defined as "slight" in severity) was endorsed by 7.2%. Moderate suicidal ideation (defined as "mild to moderate" in severity) was endorsed by 9.0%. Severe suicidal ideation (defined as "severe suicidal thoughts with intent and plan") was endorsed by 1.3%.

The proportion of individuals in each diagnostic group with suicidal ideation is presented in F1 (neurological examination score: 0=9.1%, 1=19.8%, 2=23.5%, and 3=18.5%). These proportions were found to be significantly different with the chi-square test (χ²=48.1, df=3, p<0.001). Follow-up chi-square tests among participants grouped by neurological examination score revealed a significant increase in the rate of suicidal ideation among individuals with an examination score of 1 or 2 (χ²=46.8, df=2, p<0.001) when they were compared with the participants with an examination score of 3, suggesting a diagnosis of Huntington’s disease. Additionally, the percentage of individuals with suicidal ideation significantly decreased from examination score 2 to examination score 3 (χ²=5.7, df=1, p<0.05).

The proportion of participants with definite Huntington’s disease who endorsed suicidal ideation is also presented in F1, with patients grouped by stage of illness (stage 1=16.7%, 2=21.6%, 3=19.5%, 4=14.1%, 5=9.8%). A chi-square test of independence across Huntington’s disease stage in the definite Huntington’s disease group revealed a significant difference in the percentage of individuals with suicidal ideation among stages (χ²=16.1, df=4, p<0.01). Several statistically significant post hoc chi-square comparisons among stages of Huntington’s disease were observed. A statistically significant increase in ideation was observed between stages 1 and 2 (χ²=5.5, df=1, p<0.05). The proportion of individuals with suicidal ideation subsequently decreased with each stage beyond stage 2 (χ²=13.8, df=3, p<0.01).

The average severity of suicidal ideation for each group is shown in F2. Although differences among groups based on neurological examination score were not significant, greater severity of ideation existed for diagnosed persons in later stages of disease based on functional capacity.

The current study confirms research suggesting elevated rates of suicidal ideation in persons at risk for and diagnosed with Huntington’s disease. It has been suggested that suicide in patients with Huntington’s disease occurs at a rate between seven and 200 times more often than in the general population (7, 19). Studies of suicide risk and actual completed suicide in Huntington’s disease are encumbered with methodological diversity, however, making comparisons difficult (see Stenager and Stenager [20] for a review). Autopsy studies have reported suicide rates up to 13% (12), although the most frequently cited, and average, percentage is 5.7% (7). In one of the largest studies to date, Almqvist and her colleagues (21) reported completed suicide rates in a group of 1,817 persons recruited from 100 genetic testing centers from 21 countries. Bird (22) fluently put these findings into perspective when he compared the suicide rate in Huntington’s disease of 138 of 100,000 persons per year with that of the U.S. population (i.e., 12 to 13 per 100,000 persons [23]). Not surprisingly, studies assessing suicide risk, rather than completion, report much higher rates and have indicated that suicidal ideation occurs in up to 50% of people with Huntington’s disease (11, 24–26). Although suicidal ideation is commonly considered one index of suicidal risk, few studies have demonstrated the weight of the various predictors of suicide. Indeed, our current ability to predict actual suicide is poor. Future research should attempt to validate whether suicidal ideation in Huntington’s disease patients is predictive of actual suicide attempts.

Findings from the current study are consistent with, and extend confidence in, the existent research literature. This study used the largest group size ever studied with regard to suicidal ideation in Huntington’s disease. Unlike other large studies, with survey data obtained from family members, our study directly interviewed each individual about current suicidal ideation. There are other aspects of the current study that increase our confidence in the findings. Most notably, this study involves the collaboration of 43 sites in five countries with a standardized interview measure to assess suicidal ideation, a standardized rating scale for clinical features of Huntington’s disease, and a uniform method of disease diagnosis. All study investigators were required to complete training to ensure interrater reliability of the data collection. Finally, the sample studied involves a large number of geographically diverse individuals.

Using suicidal ideation as an index of suicide risk, findings suggest two "critical" periods for increased risk of suicide in Huntington’s disease. First, the proportion of individuals with suicidal ideation more than doubled, from 9.1% in persons at risk for Huntington’s disease with a normal neurological examination to 19.8% in at-risk persons with soft neurological signs. These findings highlight the vulnerability of this particular group of genetically at-risk individuals who begin manifesting signs and experiencing symptoms of Huntington’s disease. The time around the onset of Huntington’s disease has been previously recognized as a time of high risk for suicide. For example, Di Maio and colleagues (27) compared suicide age and age of disease onset among patients who committed suicide and concluded that suicide may occur at the first appearance of Huntington’s disease symptoms. Similarly, Schoenfeld and colleagues (12) commented that the prevalence of suicide appears four times higher among suspected Huntington’s disease patients than among those who are diagnosed with definite Huntington’s disease. During the initial onset of symptoms, persons are aware of the course of the illness and are still able to plan and implement a suicide strategy. Further research is needed to characterize the personality, environmental, and biological factors associated with suicidal ideation in presymptomatic Huntington’s disease.

The clinical implications of these findings are great and suggest a major paradigm shift in clinical protocol. There is a widely held belief among clinicians that being given a diagnosis of Huntington’s disease (or other devastating diseases) will worsen depression, instill hopelessness, and increase suicidal ideation. It has been argued that delaying diagnosis of terminal, fatal, and/or devastating disease somehow protects the patient (albeit temporarily) from the trauma of the disease. Our findings suggest that these not-so-uncommon views may be false and that, indeed, the opposite may be true, where the diagnosis reduces the risk of suicide. Contrary to clinical lore, receiving the diagnosis does not seem to be associated with more suicidal ideation. Our findings show that suicidal ideation actually goes down immediately after the diagnosis of Huntington’s disease, suggesting that elevated suicide risk may be associated with the time period before diagnosis, when participants have greater uncertainty about whether they have Huntington’s disease. Perhaps the frequency of suicide may be reduced by the expedient diagnosis of Huntington’s disease combined with appropriate treatment of depression. These findings mandate further discussion and exploration to better guide current clinical practice.

A second critical period for suicide risk in Huntington’s disease occurs in the second stage of disease after diagnosis. Nearly 17% of persons in stage 1 endorsed thoughts of suicide, whereas over 21% indicated having suicidal ideation in stage 2. The second stage of Huntington’s disease is often a difficult time period, where activities may be restricted (i.e., driving, managing finances) and dependence on others for activities of daily living increases. One study examining the proportion of deaths attributed to suicide among individuals diagnosed with Huntington’s disease found that more than half of the suicides occurred in individuals showing early signs of the disease (12). It can be argued that intentions to terminate one’s life increase when one’s perception of independence dissipates.

The results suggest that certain periods during the progression of disease are associated with increases in the frequency of suicidal ideation in Huntington’s disease. These critical periods include the development of soft neurological signs before a neurological diagnosis and, after diagnosis, the initial progression of the disease, including functional decline. Although the underlying mechanisms of suicide risk in Huntington’s disease are poorly understood, it is beneficial for health care providers to be aware of periods during which patients may experience increased suicidal thoughts. Given the elevated rates of suicidal ideation in Huntington’s disease, it is essential that health care providers regularly screen for suicidal ideation during clinical assessment.

Although our findings suggest that the proportion of persons having suicide ideation diminish with advancing disease, it is striking to note that the severity of suicidal thoughts increased over this same time period. It is difficult to interpret these findings in the context of the current study. One possibility for the findings of decreased proportion with advanced stage of illness may be that people who have already committed suicide are unavailable for study. It is also possible that persons in the later stages of disease are less often queried with regard to suicidal ideation or that they experience decreased verbal fluency, making the assessment of ideation difficult to ascertain. Further research in Huntington’s disease as well as other terminal diseases may offer insight into suicide, its risk factors, and variation with disease course.

The current study has some limitations. Longitudinal study is required to better understand the relationship between suicidal ideation, illness course, and actual suicide attempts. Additionally, future studies should examine the correlates of suicidal ideation in Huntington’s disease so that possible underlying mechanisms for increased suicidal ideation might be established. For instance, it is unknown whether the presence of a major depressive disorder is associated with suicide risk in Huntington’s disease. Although the high prevalence of depression in Huntington’s disease has been well established, the nature of depression and suicidality in Huntington’s disease are poorly understood. It is unknown what proportion of persons with Huntington’s disease experience symptoms of depression secondary to biological changes in the basal ganglia and what proportion of persons are experiencing increased distress secondary to anticipation of a pending event. The interdependence of depression due to neurotransmitter regulation in the brain and depression secondary to life stressors is complex and requires further elaboration. Huntington’s disease may be a good model in which to further study the underlying mechanisms of depression and suicidality. Further research may also require efforts to better separate suicide associated with major depressive disorder from rational suicide in persons with a known terminal illness.

Participating investigators and coordinators in the Huntington Study Group were as follows: Phillipa Hedges, Elizabeth McCusker, M.D., Samantha Pearce, and Ronald Trent, Ph.D., Westmead Hospital, Sydney, New South Wales, Australia; David Abwender, Ph.D., Peter Como, Ph.D., Irenita Gardiner, R.N., Charlyne Hickey, R.N., Elise Kayson, R.N., Karl Kieburtz, M.D., Frederick Marshall, M.D., Nancy Pearson, R.N., Ira Shoulson, M.D., and Carol Zimmerman, R.N., University of Rochester, N.Y.; Elan Louis, M.D., Karen Marder, M.D., Carol Moskowitz, R.N., Carmen Polanco, B.A., Stuart Taylor, M.D., and Naomi Zubin, B.A., Columbia Presbyterian Medical Center, New York; Catherine Brown, R.N., Jill Burkeholder, Mark Guttman, M.D., Sandra Russell, Dwight Stewart, M.D., and Jackie Thomson, R.N., Markham Health Center, Toronto; Daniel S. Sax, M.D., and Marie Saint-Hilaire, M.D., Boston University, Boston; Jackie Gray, Cindy Hunter, M.S., Nanette Mercado, Ph.D., Eric Siemers, M.D., and Joanne Wojcieszek, M.D., Indiana University School of Medicine, Indianapolis; Ted Dawson, M.D., Elizabeth Leritz, B.S., Adam Rosenblatt, M.D., Meeia Sherr, R.N., and Candace Young, R.N., Johns Hopkins University, Baltimore; Tetsuo Ashizawa, M.D., Jenny Beach, R.N., and Joseph Jankovic, M.D., Baylor College of Medicine, Houston; Jeana Jaglin, R.N., and Kathleen Shannon, M.D., Rush Presbyterian/St. Luke’s Medical Center, Chicago; Anders Lundin, M.D., Karolinska Hospital, Stockholm; Kathleen Francis, M.D., and Kim Lane, University of Medicine and Dentistry of New Jersey Robert Wood Johnson Medical School, Camden; Alexander Auchus, M.D., J. Timothy Greenamyre, M.D., Steven Hersch, M.D., Randi Jones, Ph.D., and David Olson, M.D., Emory University, Atlanta; Jang-Ho John Cha, M.D., Merit Cudkowicz, M.D., Walter Koroshetz, M.D., Greg Rudolf, Paula Sexton, M.A., and Anne B. Young, M.D., Massachusetts General Hospital, Boston; Roger Albin, M.D., and Kristine Wernette, R.N., University of Michigan, Ann Arbor; Donald S. Higgins, M.D., and Carson Reider, M.S., Ohio State University, Columbus; Vicki Hunt, R.N., and Francis Walker, M.D., Bowman Gray School of Medicine, Winston-Salem, N.C.; Robert Hauser, M.D., Juan Sanchez-Ramos, M.D., and Audrey Walker, R.N., University of South Florida, Tampa; Martha Nance, M.D., Minneapolis Veterans Administration Medical Center, Minneapolis; Susan Cleary, R.N., Gina Rohs, and Oksana Suchowersky, M.D., University of Calgary Medical Center, Calgary, Alta.., Canada; Kerry Duncan and Lauren Seeberger, M.D., Colorado Neurologic Institute, Englewood; Jody Corey-Bloom, M.D., Michael Swenson, M.D., and Neal Swerdlow, M.D., University of California, San Diego; Henry Paulson, M.D., Ph.D., Robert Rodnitzky, M.D., Lynn Vining, R.N., and Jane Paulsen, Ph.D., University of Iowa, Iowa City; Wayne Martin, M.D., and Marguerite Wieler, B.Sc., P.T., University of Alberta, Edmonton, Alta., Canada; Alicia Facca, M.D., Gustavo Rey, Ph.D., and William Weiner, M.D., University of Miami, Miami; Charles Adler, M.D., John Caviness, M.D., Cindy Lied, R.N., and Stephanie Newman, R.N., Mayo Clinic, Scottsdale, Ariz.; Andrew Feigin, M.D., and Jennifer Mazurkiewicz, B.A., North Shore University Hospital, Manhasset, N.Y.; Karen Caplan, M.S.W., Janet Cellar, R.N., and Kenneth Marek, M.D., Yale University School of Medicine, New Haven, Conn.; Michael Hayden, M.D., Lynn Raymond, M.D., and Gina Rohs, University of British Columbia, Vancouver, B.C., Canada; Leon S. Dure, M.D., and Jane Lane, R.N., Children’s Hospital of Alabama, Birmingham; Diane Brown, R.N., Stewart Factor, D.O., and Eric Molho, M.D., Albany Medical College, Albany, N.Y.; Madeline Harrison, M.D., Carol Manning, Ph.D., and Elke Rost-Ruffner, R.N., University of Virginia, Charlottesville; Jonelle Adams, Ruth Cummings, R.N., and Vicki Wheelock, M.D., University of California, Davis; Richard Dubinsky, M.D., and Carolyn Gray, R.N., University of Kansas Medical Center, Kansas City; Ann Catherine Bachoud-Levi, M.D., Hôpital Henri Mondor, Creteil, France; Hartmut Meierkord, M.D., Universitatsklinikum Charite, Berlin; Joseph Friedman, M.D., and Margaret Lannon, R.N., Memorial Hospital of Rhode Island, Pawtucket; Joan Lawrence, M.D., Royal Brisbane Hospital, Brisbane, Queensland, Australia; and Allen Rubin, M.D., and Rose Schwarz, R.N., Allegheny University, Philadelphia. The biostatistics and coordination center staff were as follows: Alicia Brocht, B.A., Kathy Claude, M.S., Joshua Goldstein, Michael McDermott, Ph.D., and David Oakes, Ph.D., University of Rochester, Rochester, N.Y.

Received March 1, 2004; revisions received April 30 and June 17, 2004; accepted July 16, 2004. From the Departments of Psychiatry, Neurology, and Psychology, University of Iowa. Address correspondence and reprint requests to Dr. Paulsen, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, 1-305 Medical Education Bldg., Iowa City, IA 52241-1000; jane-paulsen@uiowa.edu (e-mail). Funded by grant 40068 from the National Institute of Neurological Disorders and Stroke, NIMH grant 01579 to Jane S. Paulsen, the Huntington’s Disease Society of America, the Huntington’s Society of Canada, Hereditary Disease Foundation grants to the Huntington Study Group, grant AG-00214 awarded to Karin Ferneyhough Hoth through the University of Iowa Center on Aging from the National Institute on Aging National Research Service Award Interdisciplinary Research Training Program on Aging, and an NIH National Research Service Award (MH-065830) to Carissa Nehl. The authors thank Beth Turner for assisting in the translation of the Huntington Study group database for the University of Iowa and Bradley McDowell, Ph.D., for statistical advice.