By Professor Guy Goodwin

  

Rapid cycling

If you experience four or more discrete episodes of depression, mania, mixed state or hypomania in a 12-month interval then you are showing rapid cycling. The definition of rapid cycling conflates patients with frequent illnesses, allowing remission between episodes, with those who cycle continuously (or switch continually) from one polarity to the other without ever being in a normal mood. Maybe 1 in 6 patients with bipolar disorder show it at some stage of their life and it is slightly more frequent if you are female, have bipolar II disorder or currently have an underactive thyroid gland. In 30-40% of cases it may be preceded by exposure to antidepressants, and worsened by treatment with antidepressants. For example, one of my patients had no episodes of depression until the age of about 50. At that point she encountered a series of troubling life events, became depressed and was treated with a tricyclic antidepressant. Subsequently she recovered but her mood then cycled between hypomania and depression every 6-8 weeks. It is very tempting to suppose that the antidepressant caused the rapid cycling but, equally, her first depressive illness could simply have been the onset, quite late in her life, of bipolar disorder. It is fair to say that opinion remains divided on which interpretation is the most correct; indeed, both may be partially so. Simply stopping the antidepressant is rarely the answer but it may be logical to try that first when this kind of pattern emerges. Rapid cycling can be very disruptive because the time spent in an unwelcome mood state mounts up much more than more severe episodes experienced less frequently. 

Mixed episodes

A mixed state refers to mania that is not simply euphoric. Some patients meet the criteria for both mania and depression simultaneously (as was required for the diagnosis in the American Diagnostic and Statistical Manual know as DSM-IV). However, an admixture of depressive mood, irritable aggression, and psychotic symptoms occurs in many manic episodes. The common patterns are: 

1. a dominant mood of severe depression with labile periods of pressured irritable hostility and paranoia, but an absence of euphoria or humour;

2. a true mixture of different moods with classical euphoria switching frequently to moderately depressed mood with anxiety and irritability.

The second type obviously has something in common with rapid cycling but is seen only as a feature of a single episode of illness, not, as for rapid cycling, as the course of many episodes over years of illness.

This traditional approach to mixed states was rather narrowly focussed on the mixture of mania with depression. In fact, the usual broad diagnostic categories like major depression, hypomania and mania all ignore a range of important additional features. For this reason, the latest version of DSM-5 (published in 2013) introduced the idea of specifiers. These are now used with any primary diagnosis (mania, hypomania, depression) to expand the clinical description. Thus, there are specifiers for mixed features, rapid cycling, anxious distress, mood congruent psychotic features, mood incongruent psychotic features, catatonia, peripartum onset, seasonal pattern and for a depressive episode, melancholic feature or atypical features. 

The way this works for the mixed features specifier is as follows. It requires the presence of three symptoms from a list restricted to those symptoms unique to the pole in question. Thus, a manic episode can now be said to have mixed features (of depression) if there are three or more of subjective depression, worry, self-reproach/guilt, negative evaluation of self, hopelessness, suicidal ideation or behaviour, anhedonia, fatigue or psychomotor retardation. A depressive episode can be said to show mixed features (of mania) if there are three or more of excited elevated mood, inflated self-esteem, pressure of speech, mind racing, increased energy/impulsivity and decreased need for sleep. The energizing aspect of the additional manic feature may increase the risk of self-harm or even suicide.

The impression is that treatment is more difficult when rapid cycling or mixed features are present. In rapid cycling there are no recommendations possible yet beyond what works for more typical bipolar disorder. In patients with manic episodes that are mixed in character, lithium may not be as effective in long-term prevention of episodes. But at present neither the existence of rapid cycling, nor of a mixed specifier, has clear positive implications for clinical care. Instead they are clues that bipolar disorder is not just one thing and that we need to be alert to how the differences may yet inform our understanding of what works best for treatment. 

If you want to read more about the diagnosis and treatment of bipolar disorder, you can download a copy of guidelines produced by the British Association for Psychopharmacology at BAP guidelines. While this is a technical document, it was written with the involvement of Bipolar UK and the intention of sharing the current consensus views with patients and their families.