A recent theory suggests that early childhood stress may affect the developing brain and cause negative effects.[47] Exposure to violence in childhood has been associated with lower school grades[48] and lower IQ in children of all races.[49] A group of largely African American urban first-grade children and their caregivers were evaluated using self-report, interview, and standardized tests, including IQ tests. The study reported that exposure to violence and trauma-related distress in young children were associated with substantial decrements in IQ and reading achievement. Exposure to Violence or Trauma lead to a 7.5-point (SD, 0.5) decrement in IQ and a 9.8-point (SD, 0.66) decrement in reading achievement.[48]