Getting irritable about irritability?

Abstract

Despite irritability being considered a symptom of several psychiatric disorders, there is no standardised definition or measurement of the construct within psychiatry. This lack of definition is in part due to a fundamental lack of understanding of what it means to be irritable and the foundational mechanisms that lead to its manifestation. This then poses a cyclical problem, whereby because the concept of irritability is poorly defined and is defined variably in different contexts, research utilising these various definitions and measures is inherently inconsistent. Hence, a new approach to studying irritability is required, one that examines the construct as being a product of tensions that arise because of discrepancies between expectations and reality. This new bottom-up definition of irritability does not rely on phenomenology alone, and therefore can be neurocognitively mapped and tested experimentally with greater precision. By establishing more sophisticated terminology and progressing to a standardised definition, the examination of irritability can progress in a meaningful way. However, this progress cannot be achieved without collaboration and multifaceted efforts from all schools of thought. Therefore, by getting irritable about irritability ourselves, we hope that a more constructive dialogue concerning this pervasive and important concept can be instigated, involving researchers from all schools of thought.

The term ‘irritability’ is variably defined. In fact, it would be fair to say that it lacks a universal, standardised definition. Instead, as reviewed in detail by Toohey and colleagues,¹ it has quite different meanings for different people, depending on the context within which it is used. Its ubiquity in psychiatric and psychological literature as a feature of both childhood and adult psychiatric disorders, reflects in part, its widespread usage in everyday life. The most galling aspect of this definitional quandary is that irritability is an experience we are all very familiar with, and yet it has proven difficult to define. There are a number of explanations as to why.

The first possibility to consider, but then promptly set aside, is that we have all assumed (incorrectly) that our personal (private) experiences of irritability are the same. Although this is certainly a possibility, it is a separate problem that applies to many phenomena and it is not particularly relevant to our present deliberations. Furthermore, because of the brevity of this piece, we naturally cannot address this question properly at this juncture, but it is nevertheless worth noting.

A second possibility is that the term is simply misused involving both the mislabelling of experiences that are not irritability and missing genuine instances of irritability that are instead subsumed by alternative terms. This scenario is also highly likely, but again it speaks to a broader problem of specificity of terminology and this is not the focus of this article. However, it warrants consideration especially as it may partly explain the seeming prevalence of irritability, both in general usage and in psychiatry and psychology.

A third possibility is that irritability is a composite of emotions (such as agitation, anger, annoyance, anxiety, confusion and frustration) and this is why it is difficult to define. This is especially so, because we do not understand which components specifically constitute irritability and each of these components are individually likely to be variable in their intensity and expression, resulting in multiple and complex combinations. Nevertheless, this is a possibility that is worth pursuing because, as we shall see, it may provide a useful model to build on.

In day-to-day life, we have all been irritable and are usually able to recognise when this occurs. Furthermore, if we examine our emotions carefully, we can also often point to the source of our irritability. But, we rarely assign the experience to ourselves—in a manner that suggests it is intrinsic (arising from within)—even though we know individuals who appear to be irritable the majority of the time—and would describe as "irritable people" (insinuating an internal cause). Thus, regarding sources of irritability, these can sometimes be obvious and direct: for example, frustration with not achieving a certain goal, or less obvious and indirect, but nevertheless explicable and attributable such as being caused by one’s ‘mood’. But, straightforward as this seems, this is where conceptualising irritability in this manner becomes complicated, because it is not immediately obvious whether the term ‘irritable mood’, for example, means irritability that stems from mood itself, as opposed to being a ‘kind’ of mood. In other words, it is both a descriptor of mood and a type of mood. This poses a significant problem, because numerous different definitions of irritability have been used across a range of contexts, making the clinical and research data concerning irritability difficult to synthesise. Therefore, attempting to distil a meaningful definition of the concept from such information is necessarily challenging and of limited use because of circularity in its derivation.^{1 2} An alternative way of defining irritability is to examine the core construct and its basic experience rather than trying to understand its nuances and variable use.

The purpose of this article is not to critique the various clinical and phenomenological definitions of irritability and determine which is the best, but instead propose that a mechanistic approach might better illuminate our thinking, and encourage further research be undertaken into understanding irritability. In psychiatry, part of the reason as to why there is a pressing need for a better understanding of irritability is that it features in several mental disorders such as mania.³ Furthermore, it is also thought to be a key factor in many childhood disorders and is linked to suicidality.⁴

Therefore, returning to the third possibility above, namely, that irritability is a composite of a number of phenomena, if we were to suppose that these separate manifestations are driven by different mechanisms, then it might help to explain both the variability and unpleasant nature of the experience. For example at its core, irritability experientially reflects a tension between an expected outcome (anticipated) and what has transpired (occurred). A straightforward example of this concerns our basic needs to eat and sleep. If these needs (expectations) are not being met in a reasonable time frame (as happens sometimes in reality), then it might lead to irritability because of a mismatch between what is happening and what was expected to happen.

Applying this reasoning to more sophisticated longer term cognitions, if one had an expectation to have achieved a certain goal in life, and this has not been met (for whatever reason), then one might be prone to being more irritable—simply because, again there is a mismatch between one’s anticipated outcome—in this case for one’s self and the reality that transpires. However, this discrepancy (mismatch) need not be driven by external events and related cognitive processes, but may instead reflect internal, biological processes which the body as a whole is striving to rectify. For example, during puberty there are significant hormonal fluctuations—reflecting a state of flux, and therefore during this period irritability may result as a consequence of the body attempting to regain stability and reach a new homeostasis. Again, one can postulate that it is the discrepancy between ‘expectation’ and ‘reality’ that may be causing the ‘sensation’ of irritability.

Critically, it is not the reasons behind this discrepancy that are important, but rather the tension which comes about as a result. Conceptualising this mismatch biologically, it may reflect a disjunction between neural processes, and it should be possible to map this tension (or disconnect) using modern-day tools, such as functional MRI. Hence, we argue that a sophisticated bottom-up definition of irritability is needed, one which can be tested and mapped more clearly than has been possible to date relying purely on phenomenology. Once mapped and given a neural basis, it could be elaborated clinically and tested in practice.

However, the primary problem, namely that of how to capture the experience of irritability in the first place, still remains. Clearly, current definitions of irritability are reliant on subjective self-report because the majority of the experience is internal and measurement requires introspective evaluation by the individual. It is only when irritability is severe that there are clear physiological and behavioural concomitants that can be observed more objectively. Therefore, an initial step would be to standardise the terminology used across all scales used to capture irritability and to do this in all contexts. That is to say, have a consensus among researchers and clinicians in the field as to the most apt definition of irritability. The ideal would be to have a definition that can be easily applied in practice while being sufficiently nuanced to capture information that informs research. This then is a useful, and in our estimation, an achievable initial goal.

Meanwhile, it is also useful to continue considering with greater granularity how irritability might manifest at a neural level. It is likely that emotion plays a core role, and its impact is linked to attention, decision-making, motivation and pleasure. In addition, anxiety and anger are also likely to contribute significantly. But it is the key interaction between expected outcomes and actuality that has to be defined across all of these constructs.

One suggestion, ours, is that irritability reflects a mismatch between components of emotion systems and that these misalignments result in an ongoing sense of irritability. By utilising a standardised and mechanistically informative definition of irritability, a framework can be created for the investigation of underlying neurobiological processes.

A potentially useful starting point for building a standard conceptualisation of irritability is the definition put forward recently by Toohey and colleagues. This definition, ‘Irritability is a mood of partial physiological agitation characterised by an increased sensitivity to sensory stimuli and a non-cognitively mediated lowered threshold for responding with anger and/or aggression to typically less vexing stimuli; it is caused by factors that directly affect physiology and/or biology such as hunger, lack of sleep, pain, and fatigue ¹ ’ captures many important elements that can be adapted further for investigational use. However, as outlined above, in order to achieve this a collaborative and multipronged effort is needed.

Hence, we encourage the investigation of irritability by all available means—making use of clinical, neuropsychological, neuroimaging and genetic tools, so that ultimately a more precise and deeper understanding of irritability can be realised. Perhaps by getting irritable about irritability, we can better define this experience and develop a more meaningful appreciation of its aetiology and clinical significance.