A role for glutathione in the pathophysiology of bipolar disorder and schizophrenia? Animal models and relevance to clinical practice.

The tripeptide, glutathione (glutamylcysteinylglycine) is the primary endogenous free radical scavenger in the human body. When glutathione (GSH) levels are reduced there is an increased potential for cellular oxidative stress, characterised by an increase and accruement of reactive oxygen species (ROS). Oxidative stress has been implicated in the pathology of schizophrenia and bipolar disorder. This could partly be caused by alterations in dopaminergic and glutamatergic activity that are implicated in these illnesses. Glutamate and dopamine are highly redox reactive molecules and produce ROS during normal neurotransmission. Alterations to these neurotransmitter pathways may therefore increase the oxidative burden in the brain. Furthermore, mitochondrial dysfunction, as a source of oxidative stress, has been documented in both schizophrenia and bipolar disorder. The combination of altered neurotransmission and this mitochondrial dysfunction leading to oxidative damage may ultimately contribute to illness symptoms. Animal models have been established to investigate the involvement of glutathione depletion in aspects of schizophrenia and bipolar disorder to further characterise the role of oxidative stress in psychopathology. Stemming from preclinical evidence, clinical studies have recently shown antioxidant precursor treatment to be effective in schizophrenia and bipolar disorder, providing a novel clinical angle to augment often suboptimal conventional treatments.

Diagnosing bipolar disorder : how can we do it better?

• Accurate diagnosis of bipolar disorder is essential for effective treatment.

• The diagnosis of bipolar disorder is particularly complex, resulting in lengthy delays between first presentation and initiation of appropriate therapy. Inappropriate therapy destabilises the course and outcome of the disease.

• Although the defining features of bipolar disorder are manic or hypomanic episodes, patients typically present for treatment of depression and commonly deny symptoms of mood elevation.

• A correct diagnosis can easily be masked by comorbidities, personality issues and complex phenomenology.

• A diagnosis of bipolar disorder can be assisted by:

   → asking about symptoms of mania or hypomania in every patient presenting with symptoms of depression.

   → recognising mixed states in which manic and depressive symptoms occur simultaneously.

   → identifying the features of bipolar depression that distinguish it from unipolar depression.

• There is a risk of over-diagnosis of bipolar disorder among patients who are histrionic, show abnormal illness behaviour MJA 2006; 184: 459–462 and/or have issues of secondary gain.

Does stage of illness impact treatment response in bipolar disorder? Empirical treatment data and their implication for the staging model and early intervention

Objective: The staging model suggests that early stages of bipolar disorder respond better to treatments and have a more favourable prognosis. This study aims to provide empirical support for the model, and the allied construct of early intervention.

Methods: Pooled data from mania, depression, and maintenance studies of olanzapine were analyzed. Individuals were categorized as having had 0, 1–5, 6–10, or >10 prior episodes of illness, and data were analyzed across these groups.

Results: Response rates for the mania and maintenance studies ranged from 52–69% and 10–50%, respectively, for individuals with 1–5 previous episodes, and from 29–59% and 11–40% for individuals with >5 previous episodes. These rates were significantly higher for the 1–5 group on most measures of response with up to a twofold increase in the chance of responding for those with fewer previous episodes. For the depression studies, response rates were significantly higher for the 1–5 group for two measures only. In the maintenance studies, the chance of relapse to either mania or depression was reduced by 40–60% for those who had experienced 1–5 episodes or 6–10 episodes compared to the >10 episode group, respectively. This trend was statistically significant only for relapse into mania for the 1–5 episode group (p = 0.005).

Conclusion: Those individuals at the earliest stages of illness consistently had a more favourable response to treatment. This is consistent with the staging model and

Setting the stage : from prodrome to treatment resistance in bipolar disorder

Bipolar disorder is common, and both difficult to detect and diagnose. Treatment is contingent on clinical needs, which differ according to phase and stage of the illness. A staging model could allow examination of the longitudinal course of the illness and the temporal impact of interventions and events. It could allow for a structured examination of the illness, which could set the stage for algorithms that are tailored to the individuals needs. A staging model could further provide as structure for assessment, gauging treatment and outcomes. The model incorporates prodromal stages and emphasizes early detection and algorithm appropriate intervention where possible. At the other end of the spectrum, the model attempts to operationalize treatment resistance. The utility of the model will need to be validated by empirical research.