More Research....

Long term cognitive development in children with prolonged crying.

Rao MR, Brenner RA, Schisterman EF, Vik T, Mills JL.

Epidemiology Branch, Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA. mr8u@nih.gov

BACKGROUND: Long term studies of cognitive development and colic have not differentiated between typical colic and prolonged crying.
OBJECTIVE: To evaluate whether colic and excessive crying that persists beyond 3 months is associated with adverse cognitive development.
DESIGN: Prospective cohort study. A sample of 561 women was enrolled in the second trimester of pregnancy. Colic and prolonged crying were based on crying behaviour assessed at 6 and 13 weeks. Children's intelligence, motor abilities, and behaviour were measured at 5 years (n = 327). Known risk factors for cognitive impairment were ascertained prenatally, after birth, at 6 and 13 weeks, at 6, 9, and 13 months, and at 5 years of age.
RESULTS: Children with prolonged crying (but not those with colic only) had an adjusted mean IQ that was 9 points lower than the control group. Their performance and verbal IQ scores were 9.2 and 6.7 points lower than the control group, respectively. The prolonged crying group also had significantly poorer fine motor abilities compared with the control group. Colic had no effect on cognitive development.

CONCLUSIONS: Excessive, uncontrolled crying that persists beyond 3 months of age in infants without other signs of neurological damage may be a marker for cognitive deficits during childhood. Such infants need to be examined and followed up more intensively.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15499048

This study is not about controlled crying, but does examine the effects of non-colic crying, which I feel can be related to cc. It can be found on this great Attachment parenting blog....
http://www.apparenting.com/research_shows_prolonged_crying_lowers_iq_in_babies.html