Postpartum psychosis is the most severe form of postpartum psychiatric illness, occurring in approximately 1 to 2 per 1000 women after childbirth. Although bipolar disorder is a risk factor for postpartum psychosis, a substantial number of women who develop postpartum psychosis have no history of psychiatric illness and experience psychiatric illness only in the context of childbearing.  What may cause or trigger postpartum psychosis in this population is not well understood.

A recent study suggests that autoimmune thyroid disease may be more common in women with postpartum psychosis.  This rationale for this study comes from the finding in several studies that thyroid abnormalities are more prevalent among women with postpartum depression.  Included in this study were 31 consecutive primiparous women with no prior psychiatric history who were admitted to an inpatient unit for the treatment of postpartum psychosis.  Because parity is a potential risk factor for thyroid autoimmunity, only primiparous women were enrolled. The control group (n = 117) consisted of primiparous women with consecutive deliveries in a community hospital practice. Blood samples were obtained at 4 weeks and 9 months postpartum. Thyroperoxidase antibody levels were quantified as immunological measures of autoimmune thyroid disease (AITD). Thyroid-stimulating hormone (TSH) and free thyroxine levels were measured to assess for thyroid dysfunction.

At 4 weeks postpartum (prior to the initiation of mood stabilizer therapy), 19% of the women with postpartum psychosis had AITD compared to only 5% of the control group.  Women with postpartum psychosis and AITD were more likely to progress to clinical thyroid dysfunction (67%) than control subjects with AITD (20%).

This study is the first to demonstrate that autoimmune thyroid disease is more prevalent in women with first-onset postpartum psychosis than in postpartum women from the general population. Furthermore, clinical thyroid dysfunction occurs significantly earlier and in a greater percentage of women with postpartum psychosis.  While this study was small in size, one of the strengths of this study was that thyroid function was assessed prior to the use of mood stabilizers, including lithium.  Based on these findings, the authors made several recommendations:

1.       Check thyroid function and autoantibody titers in all women presenting with postpartum psychosis.  It is recommended that testing occur at both 4 weeks and 6 months postpartum, as levels of autoantibodies are normally suppressed during pregnancy and often rebound after delivery.

2.       Check thyroperoxidase antibodies in women with bipolar disorder or those with a history of postpartum psychosis.  The authors hypothesized that women with elevated thyroid antibodies during pregnancy would be more likely to develop postpartum psychosis.  However, it is important to note that this hypothesis has not been formally tested, and we cannot assume that women with low levels of thyroperoxidase antibodies are not at risk for postpartum illness.  All women with histories of bipolar disorder or postpartum psychosis – regardless of their antibody status — should receive some type of prophylactic intervention and should be monitored closely after delivery.

3.       Carefully weigh the risks and benefits of using lithium in women with postpartum psychosis, particularly in women with elevated thyroperoxidase antibody titers. Elevated thyroperoxidase antibody titers and lithium treatment are both independent risk factors for the development of thyroid dysfunction; however, lithium has been shown to be highly effective for the prevention and treatment of postpartum psychosis.  This study did not have the statistical power to determine the influence of lithium treatment on risk for thyroid dysfunction.

While this study poses some interesting questions for further research, it does not substantially change the clinical management of women presenting with postpartum psychosis.  There are no well-defined treatment guidelines for this disorder; antipsychotic medications and mood stabilizers are recommended and widely used in this setting.  Whether or not a woman with postpartum psychosis has signs or symptoms suggestive of thyroid disease, the basic principles of psychiatric treatment remain the same.

Ruta Nonacs, MD PhD

 

References:

Bergink V, Kushner SA, Pop V, Kuijpens H, et al.  Prevalence of autoimmune thyroid dysfunction in postpartum psychosis. The British Journal of Psychiatry (2011) 198:264-8.

Pedersen CA, Johnson JL, Silva S, Bunevicius R, Meltzer-Brody S, Hamer RM, et al. Antenatal thyroid correlates of postpartum depression.Psychoneuroendocrinology (2007) 32: 235–45.

Robertson E, Jones I, Haque S, Holder R, Craddock N.  Risk of puerperal and non-puerperal recurrence of illness following bipolar affective puerperal (post-partum) psychosis.  The British Journal of Psychiatry (2005)186: 258-259.