background Dysregulation of the Hypothalamic Pituitary Adrenal (hpa) axis is thought to play a role in the pathogenesis of bipolar disorder (bd) (Daban e.a. 2005). Until now, most studies addressed the relationship between saliva cortisol and bd. However, measurement of cortisol in saliva is complicated by the pulsatile secretion of cortisol, the circadian rhythm of cortisol secretion and acute stress. Measurement of cortisol in scalp hair is a recently developed method tomeasure long-term cortisol  levels (Sauve e.a. 2007). In this study we evaluated the validity of cortisolin hair measurements and tested whether there is a difference in long-term cortisol levels of patients with bd and healthy controls.
aim What is the validity of this method in healthy controls? Are there differences between cortisol levels in hair of patients with bd and healthy controls?
method Scalp hair was collected from 192 healthy controls and 86 patients with bd. Hair was cut off as close to the scalp as possible and the most proximal 3 cm were used in the analysis.Methanol was used to extract cortisol from the hair samples and cortisol levels were determined using a salivary elisa cortisol kit.
results Hair cortisol levels in healthy controls were influenced by hair treatment (p=0.07), but not by gender (p=0.10), natural hair color (p = 0.25), frequency of hair wash (p = 0.26) or the use of hair products (p = 0.15). Hair cortisol levels in 28 women with long hair showed variation over time, but no overall decline of cortisol levels in consecutive segments (p = 0.25).
The data regarding cortisol levels in bd patients compared to healthy controls will be presented at the Voorjaarscongres.
conclusion These results suggest that cortisol in hair is a feasible method to measure long-term cortisol levels in research settings.