Projection du fardeau du cancer au Canada en 2024.

CONTEXTE: Les données de surveillance du cancer sont essentielles pour mieux comprendre les lacunes et les progrès réalisés dans la lutte contre le cancer. Nous avons cherché à résumer les répercussions prévues du cancer au Canada en 2024, en effectuant des projections sur les nouveaux cas de cancer et les décès par cancer, par sexe et par province ou territoire, pour tous les âges confondus. MÉTHODES: Nous avons obtenu les données sur les nouveaux cas de cancer (c.-à-d., l'incidence, 1984­2019) et les décès par cancer (c.-à-d., la mortalité, 1984­2020) du Registre canadien du cancer et de la Base canadienne de données de l'état civil ­ Décès, respectivement. Nous avons projeté les chiffres et les taux d'incidence du cancer et de mortalité jusqu'en 2024 pour 23 types de cancer, par sexe et par province ou territoire. Nous avons calculé des taux normalisés selon l'âge au moyen de données de la population type canadienne de 2011. RÉSULTATS: En 2024, les nombres de nouveaux cas de cancer et de décès causés par le cancer devraient atteindre 247 100 et 88 100, respectivement. Le taux d'incidence normalisé selon l'âge (TINA) et le taux de mortalité normalisé selon l'âge (TMNA) devraient diminuer légèrement par rapport aux années précédentes, tant chez les hommes que chez les femmes, avec des taux plus élevés chez les hommes (TINA de 562,2 pour 100 000, et TMNA de 209,6 pour 100 000 chez les hommes; TINA de 495,9 pour 100 000 et TMNA de 152,8 pour 100 000 chez les femmes). Les TINA et les TMNA de plusieurs cancers courants devraient continuer à diminuer (p. ex., cancer du poumon, cancer colorectal et cancer de la prostate), tandis que ceux de plusieurs autres cancers devraient augmenter (p. ex., cancer du foie et des voies biliaires intrahépatiques, cancer du rein, mélanome et lymphome non hodgkinien). INTERPRÉTATION: Bien que l'incidence globale du cancer et la mortalité connexe sont en déclin, il devrait y avoir une augmentation des nouveaux cas et des décès au Canada en 2024, en grande partie en raison de la croissance et du vieillissement de la population. Les efforts en matière de prévention, de dépistage et de traitement ont atténué les répercussions de certains cancers, mais ces projections à court terme soulignent l'effet potentiel du cancer sur les gens et les systèmes de soins de santé au Canada.

Projected estimates of cancer in Canada in 2024.

BACKGROUND: Cancer surveillance data are essential to help understand where gaps exist and progress is being made in cancer control. We sought to summarize the expected impact of cancer in Canada in 2024, with projections of new cancer cases and deaths from cancer by sex and province or territory for all ages combined. METHODS: We obtained data on new cancer cases (i.e., incidence, 1984-2019) and deaths from cancer (i.e., mortality, 1984-2020) from the Canadian Cancer Registry and Canadian Vital Statistics Death Database, respectively. We projected cancer incidence and mortality counts and rates to 2024 for 23 types of cancer, overall, by sex, and by province or territory. We calculated age-standardized rates using data from the 2011 Canadian standard population. RESULTS: In 2024, the number of new cancer cases and deaths from cancer are expected to reach 247 100 and 88 100, respectively. The age-standardized incidence rate (ASIR) and mortality rate (ASMR) are projected to decrease slightly from previous years for both males and females, with higher rates among males (ASIR 562.2 per 100 000 and ASMR 209.6 per 100 000 among males; ASIR 495.9 per 100 000 and ASMR 152.8 per 100 000 among females). The ASIRs and ASMRs of several common cancers are projected to continue to decrease (i.e., lung, colorectal, and prostate cancer), while those of several others are projected to increase (i.e., liver and intrahepatic bile duct cancer, kidney cancer, melanoma, and non-Hodgkin lymphoma). INTERPRETATION: Although the overall incidence of cancer and associated mortality are declining, new cases and deaths in Canada are expected to increase in 2024, largely because of the growing and aging population. Efforts in prevention, screening, and treatment have reduced the impact of some cancers, but these short-term projections highlight the potential effect of cancer on people and health care systems in Canada.

Incidence of Breast Cancer in Younger Women: A Canadian Trend Analysis.

Purpose: Breast cancer (BC) incidence is increasing globally. Age-specific BC incidence trend analyses are lacking for women under age 50 in Canada. In this study, we evaluate the incidence trends in breast cancer in women under age 50 in Canada and compare them with corresponding trends among women 50 to 54. Methods: BC case counts were obtained from the National Cancer Incidence Reporting System (1984-1991) and the Canadian Cancer Registry (1992-2019) both housed at Statistics Canada. Population data were also obtained from Statistics Canada. Annual female BC age-specific incidence rates from 1984 to 2019 were derived for the following age groups: 20 to 29, 30 to 39, 40 to 49, 40 to 44, 45 to 49, and 50 to 54. Changes in trends in age-specific BC incidence rates, if any, and annual percent changes (APCs) for each identified trend, were determined using JoinPoint. Results: Statistically significant increasing trends in BC incidence rates were noted for almost all age groups: since 2001 for 20 to 29 (APC = 3.06%, P < .001); since 2009 for 30 to 39 (APC = 1.25%, P = .007); since 1984 for both 40 to 49 (APC = 0.26%, P < .001) and 40 to 44 (APC = 0.19%, P = .011), increased since 2015 for 40 to 49 (APC = 0.77%, P = .047); and since 2005 for 50 to 54 (APC = 0.38%, P = .022). Among women 45 to 49 there was a non-significant increase since 2005 (APC = 0.24, P = .058). Statistically significant average annualized increases in BC incidence rates were observed for each age group studied. Conclusions: Examining age-specific incidence rates formed a more complete picture of BC time trends with significant increasing trends in the incidence of BC among women in their 20s, 30s, 40s, and early 50s. A greater awareness regarding the increasing number of cases of BC in women younger than 50 is critical to allow for earlier diagnosis with its resultant reduced mortality and morbidity.

Progress in site-specific cancer mortality in Canada over the last 70 years.

In Canada, the absolute number of cancer deaths has been steadily increasing, however, age-standardized cancer mortality rates peaked decades ago for most cancers. The objective of this study was to estimate the reduction in deaths for each cancer type under the scenario where peak mortality rates had remained stable in Canada. Data for this study were obtained the Global Cancer Observatory and Statistics Canada. We estimated age-standardized mortality rates (ASMR, per 100,000) from 1950 to 2022, standardized to the 2011 Canadian standard population. We identified peak mortality rates and applied the age-specific mortality rates from the peak year to the age-specific Canadian population estimates for subsequent years (up to 2022) to estimate the number of expected deaths. Avoided cancer deaths were the difference between the observed and expected number of cancer deaths. There have been major reductions in deaths among cancers related to tobacco consumption and other modifiable lifestyle habits (417,561 stomach; 218,244 colorectal; 186,553 lung; 66,281 cervix; 32,732 head and neck; 27,713 bladder; 22,464 leukemia; 20,428 pancreas; 8863 kidney; 3876 esophagus; 290 liver). There have been 201,979 deaths avoided for female-specific cancers (breast, cervix, ovary, uterus). Overall, there has been a 34% reduction in mortality for lung cancer among males and a 9% reduction among females. There has been a significant reduction in cancer mortality in Canada since site-specific cancer mortality rates peaked decades ago for many cancers. This shows the exceptional progress made in cancer control in Canada due to substantial improvements in prevention, screening, and treatment. This study highlights priority areas where more attention and investment are needed to achieve progress.

Progress in cancer control leads to a substantial number of cancer deaths avoided in Canada.

It is currently not known how many more cancer deaths would have occurred among Canadians if cancer mortality rates were unchanged following various modern human interventions. The objective of this study was to estimate the number of cancer deaths that have been avoided in Canada since the age-standardized overall cancer mortality rate peaked in 1988. We applied the age-specific overall cancer mortality rates from 1988 to the Canadian population for all subsequent years to estimate the number of expected deaths. Avoided cancer deaths were estimated as the difference between the observed and expected number of cancer deaths for each year. Since 1988, there have been 372 584 (standardized mortality ratio = 0.77) and 120 045 (standardized mortality ratio = 0.90) avoided cancer deaths in males and females, respectively (492 629 total). Nearly half a million cancer deaths have been avoided in Canada since the overall cancer mortality rate peaked, which demonstrates the exceptional progress made in modern cancer control in Canada.

Lifetime probability of developing cancer and dying from cancer in Canada, 1997 to 2020.

Background: The lifetime probabilities of developing (LPdev) cancer and dying (LPdying) from cancer are useful summary statistics that describe the impact of cancer within a population. This study aims to present detailed LPdev and LPdying for cancer by sex and cancer type and to describe changes in these lifetime probabilities over time among the Canadian population. Data and methods: Cancer incidence data (1997 to 2018) were obtained from the Canadian Cancer Registry. All-cause and cancer mortality data (1997 to 2020) were obtained from the Canadian Vital Statistics - Death Database. LPdev and LPdying were calculated using the DevCan software, and trends over time were estimated using Joinpoint. Results: The LPdev for all cancers combined was 44.3% in Canada in 2018, with all results excluding Quebec. At the age of 60, the conditional probability of developing cancer was very similar (44.0% for males and 38.2% for females). The LPdying was 22.5% among the Canadian population in 2020, while the probability of dying from cancer conditional on surviving until age 60 was 25.1% for males and 20.5% for females. Generally, males experienced higher LPdev and LPdying for most specific cancers compared with females. Interpretation: LPdev and LPdying for cancer mirror cancer incidence and mortality rates. Cancer-specific changes in these probabilities over time are indicative of the cancer trends resulting from cancer prevention, screening, detection, and treatment. These changes in LPdev and LPdying provide insight into the shifting landscape of the Canadian cancer burden.

Impact of Breast Cancer Screening on 10-Year Net Survival in Canadian Women Age 40-49 Years.

PURPOSE: In Canada, some provincial/territorial mammography screening programs include women age 40-49 years, whereas others do not. This study examines the impact of this dichotomy on the 10-year breast cancer (BC) net survival (NS) among women age 40-49 years and 50-59 years at diagnosis. METHODS: Using the Canadian Cancer Registry data record linked to death information, we evaluated the cohort of Canadian women age 40-49 years and 50-59 years diagnosed with BC from 2002 to 2007. We compared 10-year NS estimates in the jurisdictions with organized screening programs that included women age 40-49 years, designated as screeners (Northwest Territories, British Columbia, Alberta, Nova Scotia, and Prince Edward Island), with comparator programs that did not (Yukon, Manitoba, Saskatchewan, Ontario, Quebec, New Brunswick, and Newfoundland and Labrador). RESULTS: BC was the primary cause of 10-year mortality in women age 40-49 years diagnosed with BC (90.7% of deaths). Among these women, the 10-year NS for screeners (84.8%; 95% CI, 83.8 to 85.8) was 1.9 percentage points (pp) higher than that for comparators (82.9%; 95% CI, 82.3 to 83.5; P = .001). The difference in favor of screeners was significant among women age 45-49 years (2.6 pp; P = .001) but not among women age 40-44 years (0.9 pp; P = .328). Similarly, the incidence-based BC mortality rate was significantly lower in screener jurisdictions among women age 40-49 years and 45-49 years, but not for 40-44 years. Provincial/territorial NS increased significantly with higher mammography screening participation (P = .003). The BC incidence rate was virtually identical in screener and comparator jurisdictions among women age 40-49 years (P = .976) but was significantly higher for comparators among women age 50-59 years (P < .001). CONCLUSION: Screening programs that included women in their 40s were associated with a significantly higher BC 10-year NS in women age 40-49 years, but not an increased rate of BC diagnosis. These results may inform screening guidelines for women age 40-49 years.

The Impact of Organised Screening Programs on Breast Cancer Stage at Diagnosis for Canadian Women Aged 40-49 and 50-59.

The relationship between Canadian mammography screening practices for women 40−49 and breast cancer (BC) stage at diagnosis in women 40−49 and 50−59 years was assessed using data from the Canadian Cancer Registry, provincial/territorial screening practices, and screening information from the Canadian Community Health Survey. For the 2010 to 2017 period, women aged 40−49 were diagnosed with lesser relative proportions of stage I BC (35.7 vs. 45.3%; p < 0.001), but greater proportions of stage II (42.6 vs. 36.7%, p < 0.001) and III (17.3 vs. 13.1%, p < 0.001) compared to women 50−59. Stage IV was lower among women 40−49 than 50−59 (4.4% vs. 4.8%, p = 0.005). Jurisdictions with organised screening programs for women 40−49 with annual recall (screeners) were compared with those without (comparators). Women aged 40−49 in comparator jurisdictions had higher proportions of stages II (43.7% vs. 40.7%, p < 0.001), III (18.3% vs. 15.6%, p < 0.001) and IV (4.6% vs. 3.9%, p = 0.001) compared to their peers in screener jurisdictions. Based on screening practices for women aged 40−49, women aged 50−59 had higher proportions of stages II (37.2% vs. 36.0%, p = 0.003) and III (13.6% vs. 12.3%, p < 0.001) in the comparator versus screener groups. The results of this study can be used to reassess the optimum lower age for BC screening in Canada.

Projected estimates of cancer in Canada in 2022.

BACKGROUND: Regular cancer surveillance is crucial for understanding where progress is being made and where more must be done. We sought to provide an overview of the expected burden of cancer in Canada in 2022. METHODS: We obtained data on new cancer incidence from the National Cancer Incidence Reporting System (1984-1991) and Canadian Cancer Registry (1992-2018). Mortality data (1984-2019) were obtained from the Canadian Vital Statistics - Death Database. We projected cancer incidence and mortality counts and rates to 2022 for 22 cancer types by sex and province or territory. Rates were age standardized to the 2011 Canadian standard population. RESULTS: An estimated 233 900 new cancer cases and 85 100 cancer deaths are expected in Canada in 2022. We expect the most commonly diagnosed cancers to be lung overall (30 000), breast in females (28 600) and prostate in males (24 600). We also expect lung cancer to be the leading cause of cancer death, accounting for 24.3% of all cancer deaths, followed by colorectal (11.0%), pancreatic (6.7%) and breast cancers (6.5%). Incidence and mortality rates are generally expected to be higher in the eastern provinces of Canada than the western provinces. INTERPRETATION: Although overall cancer rates are declining, the number of cases and deaths continues to climb, owing to population growth and the aging population. The projected high burden of lung cancer indicates a need for increased tobacco control and improvements in early detection and treatment. Success in breast and colorectal cancer screening and treatment likely account for the continued decline in their burden. The limited progress in early detection and new treatments for pancreatic cancer explains why it is expected to be the third leading cause of cancer death in Canada.

Short-term cancer prevalence in Canada, 2018.

BACKGROUND: As the leading cause of death in Canada, cancer imposes an enormous burden on both the health of Canadians and the Canadian health care system. This study presents detailed tumour-based cancer prevalence estimates in Canada by sex, age group, cancer type and prevalence duration as of January 1, 2018. DATA AND METHODS: Estimates of two- and five-year cancer prevalence were calculated for an extensive list of cancers in the Canadian population (excluding Quebec) based on incidence data from the Canadian Cancer Registry linked to mortality data from the Canadian Vital Statistics - Death Database, and death-related information from tax data. RESULTS: The two- and five-year cancer prevalence counts were 236,785 (832.1 per 100,000 people) and 503,060 (1,767.8 per 100,000 people), respectively. Cancer prevalence estimates varied by cancer site, and the four most prevalent cancers (breast, prostate, colorectal, lung) accounted for 49.6% of total five-year cancer prevalence in Canada. Prevalence for all cancers combined increased dramatically with age: 74.3% of prevalent cases among males and 61.9% among females were encountered among the population aged 60 and older. Prevalence was higher among females than males before age 60, and higher among males thereafter, peaking in the 80-to-89 age group for both sexes. INTERPRETATION: Prevalence mirrors the effects of both cancer incidence and survival. Breaking down cancer prevalence by disease duration is useful to distinguish groups of patients in different phases of care. An increase in prevalence indicates a greater demand for health care services and translates into a significant economic burden for the jurisdictions that are responsible for providing such services.

Fast food intake in Canada: Differences among Canadians with diverse demographic, socio-economic and lifestyle characteristics.

OBJECTIVES: To estimate the contribution of fast food to daily energy intake, and compare intake among Canadians with varied demographic, socioeconomic and lifestyle characteristics. METHODS: Using the National Cancer Institute method, nationally representative estimates of mean usual daily caloric intake from fast food were derived from 24-hour dietary recall data from the Canadian Community Health Survey Cycle 2.2 (n = 17,509) among participants age ≥ 2 years. Mean daily intake and relative proportion of calories derived from fast food were compared among respondents with diverse demographic (age, sex, provincial and rural/urban residence), socio-economic (income, education, food security status) and health and lifestyle characteristics (physical activity, fruit/vegetable intake, vitamin/ mineral supplement use, smoking, binge drinking, body mass index (BMI), self-rated health and dietary quality). RESULTS: On average, Canadians reported consuming 146 kcal/day from fast food, contributing to 6.3% of usual energy intake. Intake was highest among male teenagers (248 kcal) and lowest among women ≥ 70 years of age (32 kcal). Fast food consumption was significantly higher among respondents who reported lower fruit and vegetable intake, poorer dietary quality, binge drinking, not taking vitamin/mineral supplements (adults only), and persons with higher BMI. Socio-economic status, physical activity, smoking and self-rated health were not significantly associated with fast food intake. CONCLUSION: While average Canadian fast food consumption is lower than national US estimates, intake was associated with lower dietary quality and higher BMI. Findings suggest that research and intervention strategies should focus on dietary practices of children and adolescents, whose fast food intakes are among the highest in Canada.

A Comparison of Dietary Practices at or En Route to School between Elementary and Secondary School Students in Vancouver, Canada.

BACKGROUND: There is evidence that dietary quality declines as children age in North America, but few studies have explored whether food environment exposures in secondary schools as opposed to elementary schools are associated with changes in students' school-day food choices. METHODS: This study examined differences in dietary practices (at or en route to and/or from school) between students in their last years of elementary school (grades 5 to 7) and first year of secondary school (grade 8) in Vancouver, Canada, controlling for sociodemographic characteristics and school-level socioeconomic status. Demographic characteristics and dietary data were collected through a cross-sectional survey (n=950 from 26 schools) and combined with school-level socioeconomic data derived from the 2006 Canadian Census. RESULTS: Multilevel logistic regression analyses indicated that secondary school students were significantly more likely to report daily consumption of fast foods (odds ratio=1.92; 95% CI 1.18 to 3.12) and minimally nutritious packaged snacks (eg, candy or chocolate bars) (odds ratio=1.60; 95% CI 1.05 to 2.45), and to report regular purchases from off-campus retailers (odds ratio=1.63; 95% CI 1.10 to 2.42). Gender, food insecurity, lower acculturation to Canada, and access to more weekly spending money were associated with nutritionally poor practices. Students attending schools drawing from lower-income neighborhoods were also significantly more likely to consume fast foods and packaged snacks daily. The majority of students sampled did not report consuming healthy foods, such as fruit and vegetables, daily at or en route to and/or from school. Intake of fruit, vegetables, and low-fat milk did not differ significantly between elementary and secondary school students. CONCLUSIONS: Findings suggest that research and intervention strategies should address modifiable school-level exposures and policies to improve dietary practices for both elementary and secondary school-aged youth, while at the same time addressing sociocultural factors associated with eating behavior.

Do Canadians meet Canada's Food Guide's recommendations for fruits and vegetables?

National dietary guidelines pertaining to the intake of fruits and vegetables (FV) were recently amended, in both Canada and the United States, to provide specific recommendations about dark green and orange vegetables and juice consumption. However, little is known about the extent to which Canadians meet the updated recommendations for FV. This study fills current gaps by applying the National Cancer Institute's methodology for assessing the distribution of usual intake of foods to examine reported FV intake using 24-h recalls from the 2004 Canadian Community Health Survey, cycle 2.2, a nationally representative health survey. After identifying plausible respondents, usual intake distributions were estimated after adjustment for respondents' age, sex, body mass index, frequency of FV consumption, sequence effect, weekend-weekday effect, income, and ethnicity. The majority of Canadians did not meet Health Canada's 2007 recommendations for FV intake. Only 26% of the population aged 2 years and older consumed the minimum number of daily servings recommended for their respective age-sex group. Approximately 1 in 5 Canadians consumed at least 1 daily serving of dark green vegetables, and 9% consumed 1 or more daily servings of orange vegetables or their substitutes. Juice was a substantial contributor to FV intake, particularly for children and teens who, on average, consumed 32%-41% of their daily FV servings as juice. These findings provide insight into the quantity and composition of FV intake and adherence to national dietary recommendations in Canada.

Relationships between neighborhoods, physical activity, and obesity: a multilevel analysis of a large Canadian city.

In Canada, there is limited research examining the associations between objectively measured neighborhood environments and physical activity (PA) and obesity. The purpose of this study was to determine the relationships between variables from built and social environments and PA and overweight/obesity across 86 Ottawa, Canada neighborhoods. Individual-level data including self-reported leisure-time PA (LTPA), height, and weight were examined in a sample of 4,727 adults from four combined cycles (years 2001/03/05/07) of the Canadian Community Health Survey (CCHS). Data on neighborhood characteristics were obtained from the Ottawa Neighbourhood Study (ONS); a large study of neighborhoods and health in Ottawa, Canada. Binomial multivariate multilevel models were used to examine the relationships between environmental and individual variables with LTPA and overweight/obesity using survey weights in men and women separately. Within the sample, ~75% of the adults were inactive (<3.0 kcal/kg/day) while half were overweight/obese. Results of the multilevel models suggested that for females greater park area was associated with increased odds of LTPA and overweight/obesity. Greater neighborhood density of convenience stores and fast food outlets were associated with increased odds of females being overweight/obese. Higher crime rates were associated with greater odds of LTPA in males, and lower odds of male and female overweight/obesity. Season was significantly associated with PA in men and women; the odds of LTPA in winter months were half that of summer months. Findings revealed that park area, crime rates, and neighborhood food outlets may have different roles with LTPA and overweight/obesity in men and women and future prospective studies are needed.

A multilevel analysis of neighbourhood built and social environments and adult self-reported physical activity and body mass index in Ottawa, Canada.

Canadian research examining the combined effects of social and built environments on physical activity (PA) and obesity is limited. The purpose of this study was to determine the relationships among built and social environments and PA and overweight/obesity in 85 Ottawa neighbourhoods. Self-reported PA, height and weight were collected from 3,883 adults using the International PA Questionnaire from the 2003-2007 samples of the Rapid Risk Factor Surveillance System. Data on neighbourhood characteristics were obtained from the Ottawa Neighbourhood Study; a large study of neighbourhoods and health in Ottawa. Two-level binomial logistic regression models stratified by sex were used to examine the relationships of environmental and individual variables with PA and overweight/obesity while using survey weights. Results identified that approximately half of the adults were insufficiently active or overweight/obese. Multilevel models identified that for every additional convenience store, men were two times more likely to be physically active (OR = 2.08, 95% CI: 1.72, 2.43) and with every additional specialty food store women were almost two times more likely to be overweight or obese (OR = 1.77, 95% CI: 1.33, 2.20). Higher green space was associated with a reduced likelihood of PA (OR = 0.93, 95% CI: 0.86, 0.99) and increased odds of overweight and obesity in men (OR = 1.10, 95% CI: 1.01, 1.19), and decreased odds of overweight/obesity in women (OR = 0.66, 95% CI: 0.44, 0.89). In men, neighbourhood socioeconomic scores, voting rates and sense of community belonging were all significantly associated with overweight/obesity. Intraclass coefficients were low, but identified that the majority of neighbourhood variation in outcomes was explained by the models. Findings identified that green space, food landscapes and social cohesiveness may play different roles on PA and overweight/obesity in men and women and future prospective studies are needed.

Prevalence and correlates of multiple victimization in a nation-wide adolescent sample.

OBJECTIVES: Adolescents often experience different types of victimization across a specified period of time in different situations. These multiple victimization experiences can have a number of deleterious effects on psychosocial well-being. To expand on research gathered primarily from US samples, the current study estimated the prevalence of multiple victimization in a nationally representative sample of Canadian adolescents. We also expanded on past research by adopting an ecological approach to identify correlates of multiple victimization. METHODS: Cross-sectional data from the 2000-2001 cycle of the National Longitudinal Survey of Children and Youth (NLSCY) were used to estimate the prevalence of multiple victimization (verbal harassment, threat of and actual physical assault, school social exclusion, discrimination) in 1,036 13-16 year olds. We also examined household (e.g., parental education), family (e.g., parenting practices), and adolescent (e.g., friendship quality) correlates of multiple victimization for the whole sample and separately by sex. RESULTS: Among the 6 in 10 adolescents who reported at least 1 victimization experience, 30.5% reported 2 types of victimization whereas 23.7% reported 3 or more types. There was an increased probability of multiple victimization (2 or more types) in adolescents who reported greater parental rejection, who engaged in more frequent out-of-school activities, and who experienced non-victimization adversity. The probability decreased if adolescents reported greater friendship quality. CONCLUSIONS: The clustering of different types of victimization is common among adolescents. For both males and females, a difficult parent-child relationship characterized as rejecting is important when considering risk for multiple victimization, as is the adolescent's functioning outside of the home in the context of friendship quality and involvement in out-of-school activities. Non-victimization adversity (e.g., death of a loved one) also emerged as a significant multiple victimization correlate. PRACTICE IMPLICATIONS: Non-physically invasive types of victimization (although adolescents also endorsed physical assault) are a reality for a number of adolescents. As such, we need to inquire about such experiences as school social exclusion, discrimination, and verbal threats in applied contexts. Moreover, in order to better identify adolescents who may be vulnerable to multiple forms of victimization, we need to adopt an ecological approach that considers individual, family, and household functioning.

Diagnosing zygosity in infant twins: physical similarity, genotyping, and chorionicity.

We compared the results of different methods for diagnosing zygosity in a sample of 237 same-sex pairs of twins assessed at 5 and 18 months of age. Despite the twins' very young age and early stage of development, physical similarity was concordant with genotyping in 91.9% of cases at 5 months and 93.8% of cases at 18 months, for a subsample of 123 and 113 pairs, respectively. This concordance rate was obtained following a case-by-case assessment of each pair's physical similarity using a shortened version of the Zygosity Questionnaire for Young Twins (Goldsmith, 1991). Taking into account the chorionicity data available from the twins' medical files, we were able to classify correctly 96% of the pairs, an accuracy rate comparable to previously reported rates obtained with older twins. Chorionicity data is especially useful since we found that monochorionic MZ twins are more difficult than dichorionic MZ twins to diagnose by physical similarity at these young ages. The relative cost-benefit of methods based on reported physical similarity and DNA analysis is discussed in light of these results.