A long-term study demonstrated that the risks of medical and social disabilities extend into adulthood and are higher with decreasing gestational age at birth and include cerebral palsy, intellectual disability, disorders of psychological development, behavior, and emotion, disabilities of vision and hearing, and epilepsy.[134] Standard intelligence tests showed that 41 percent of children born between 22 and 25 weeks had moderate or severe learning disabilities when compared to the test scores of a group of similar classmates who were born at full-term.[3] It is also shown that higher levels of education were less likely to be obtained with decreasing gestational age at birth.[134] People born prematurely may be more susceptible to developing depression as teenagers.[135] Some of these problems can be described as being within the executive domain and have been speculated to arise due to decreased myelinization of the frontal lobes.[136] Studies of people born premature and investigated later with MRI brain imaging, demonstrate qualitative anomalies of brain structure and grey matter deficits within temporal lobe structures and the cerebellum that persist into adolescence.[137] Throughout life they are more likely to require services provided by physical therapists, occupational therapists, or speech therapists.[133]