Researchers from the University of New Mexico in Albuquerque addressed the issue of anxiety, fatigue and emotional stress interfering with the ability of new mothers of premature infants to express milk for their babies in the NICU (newborn intensive care unit).
To facilitate the breast-feeding experience, intervention mothers were given a 20-minute audio cassette tape based on relaxation and visual imagery techniques.

At a single follow-up expression of milk at the hospital approximately 1 week after enrollment, these mothers expressed 63% more breast milk than a randomized group of control mothers.
The fat content of the breast milk in the two groups was not significantly different. Among a small group of mothers whose infants were receiving mechanical ventilation, the increase in milk volume compared with that of control mothers was 121%.
Longer-term effects of the relaxation/imagery approach (such as extending the duration of breast-feeding or reducing parental stress after hospital discharge) and the physiologic basis for the increased volume of expressed milk (improved milk production v more efficient milk ejection) are appropriate topics for future research.

Citation:  Feher SD, Berger LR, Johnson JD, Wilde JB. Increasing breast milk production for premature infants with a relaxation/imagery audiotape. Pediatrics. 1989 Jan;83 (1):pages 57-60.