Borderline Intellectual Functioning: A Systematic Literature Review Minna Peltopuro, Timo Ahonen, Jukka Kaartinen, Heikki Seppa ¨la ¨, and Vesa Na ¨rhi Abstract The literature related to people with borderline intellectual functioning (BIF) was systematically reviewed in order to summarize the present knowledge. Database searches yielded 1,726 citations, and 49 studies were included in the review. People with BIF face a variety of hardships in life, including neurocognitive, social, and mental health problems. When adults with BIF were compared with the general population, they held lower-skilled jobs and earned less money. Although some risk factors (e.g., low birth weight) and preventive factors (e.g., education) were reported, they were not specific to BIF. The review finds that, despite the obvious everyday problems, BIF is almost invisible in the field of research. More research, societal discussion, and flexible support systems are needed. Key Words: borderline intellectual functioning; mild cognitive limitations; slow learners; systematic literature review People with borderline intellectual functioning (BIF) have an IQ test score that is one to two standard deviations below average, in the range of 70 to 85. If normal distribution of intelligence is considered, 13.6% of the population fits into that category. Not all of the people who score in this IQ range have problems with adaptive behavior (conceptual, social, and practical skills), nor do they all need support, but this figure can be used as a guide. Despite the high percentage of people in this category, BIF is a rarely studied topic. When it is included in studies, the focus of the research is often on people with mild intellectual disability (MID) or a specific learning disability (SLD), and the BIF group is either combined with these or treated as a control group. There seem to be two traditions examining BIF: medical and pedagogical. Generally speaking, the medical tradition concentrates on BIF as a consequence of some medical condition, and the pedagogical tradition concentrates on the difficulties of teaching children with BIF. A research tradition focusing on BIF for its own sake, however, is lacking. There is also no unanimous term for the phenomenon of BIF, and it has had numerous names in the past. The names used in the literature include, for example, borderline mental retardation, slow learner, mild cognitive impairment, and general learning disability. Historically, there has been interest in BIF in the intellectual disability (ID) community in the late 1960s and again in the late 1990s. In the 1960s, the American Association on Intellectual and Developmental Disabilities (AAIDD; formerly called the American Association on Mental Retardation) defined those with an IQ test score of 70 to 85 as eligible for classification as mentally retarded (Heber, 1959, 1961). The report by the President’s Committee on Mental Retardation (PCMR), ‘‘The Six-Hour Retarded Child,’’ identi- fied the group of children who were labeled as mentally retarded during school hours based solely on an IQ test score without regard to their adaptive behavior (President’s Committee on Mental Retar- dation, 1969). Outside the academic setting, however, these children seemed to manage reason- ably well. The report was also concerned with overrepresentation of ethnic groups and poverty among those children labeled as mentally retarded. In the early 1970s, the classification system around mental retardation was modified, and BIF was removed from the diagnostic category (Grossman, 1973). Three decades later, the PCMR revisited ‘‘The Six-Hour Retarded Child’’ in a report and INTELLECTUAL AND DEVELOPMENTAL DISABILITIES 2014, Vol. 52, No. 6, 419–443 ’AAIDD DOI: 10.1352/1934-9556-52.6.419 M. Peltopuro et al. 419