How about this?

Breast milk levels of cortisol and Secretory Immunoglobulin A (SIgA) differ 
with maternal mood and infant neuro-behavioral functioning.
Sybil Hart, , a, L. Mallory Boylanb, Barbara Borderc, Sebrina R. Carrolld, 
Daniel McGuneglee and Richard M. Lampe
Infant Behavior and Development Volume 27, Issue 1, February 2004, Pages 
101-106

<http://www.earlyhumandevelopment.com/article/S0378-3782%2807%2900004-7/abstract>

This is the conclusion:
"The findings are consistent with our proposal that exposure to cortisol in 
breast milk influences infant temperament. Biologically active components in 
breast milk may represent one avenue through which the mother shapes the 
development of the human infant during the postnatal period."

Which is NOT to say that a stressed mother should wean her baby.  My word, 
what a bizarre idea.

As as aside, there is another interesting cortisol study, but irrelevant to 
'our' naturopath's idea of weaning to relieve stress:

Changes in the concentration of cortisol in milk during different stages of 
human lactation.
Kulski JK, Hartmann PE.
Aust J Exp Biol Med Sci. 1981 Dec;59(Pt 6):769-78.

<http://www.ncbi.nlm.nih.gov/pubmed/7340774>

"...it is possible that cortisol in breast milk may help to control the 
transport of fluids and salts from the gastrointestinal tract of infants."

Jacquie Nutt IBCLC
South Africa 

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