A sigh of relief actually confers relaxation

The Psychophysiology of the Sigh: II: The Sigh From the Psychological Perspective. Elke V lemincx, Liza Severs, Jan-Marino Ramirez. Biological Psychology, July 6 2022, 108386. https://doi.org/10.1016/j.biopsycho.2022.108386

Highlights

• Sighs have essential regulatory functions.

• Sighs may function as psychophysiological resetters.

• Sighs may contribute to psychophysiological flexibility.

Abstract

A sigh is a distinct respiratory behavior with specific psychophysiological roles. In two accompanying reviews we will discuss the physiological and psychological functions of the sigh. The present review will focus on the psychological functions of the sigh. We discuss the regulatory effects of a sigh, and argue how these effects may become maladaptive when sighs occur excessively. The adaptive role of a sigh is discussed in the context of regulation of psychophysiological states. We propose that sighs facilitate transitions from one psychophysiological state to the next, and this way contribute to psychophysiological flexibility, via a hypothesized resetting mechanism. We discuss how a sigh resets respiration, by controlling mechanical and metabolic properties of respiration associated with respiratory symptoms. Next, we elaborate on a sigh resetting emotional states by facilitating emotional transitions.

We attempt to explain the adaptive and maladaptive functions of a sigh in the framework of stochastic resonance, in which we propose occasional, spontaneous sighs to be noise contributing to psychophysiological regulation, while excessive sighs result in psychophysiological dysregulation. In this context, we discuss how sighs can contribute to therapeutic interventions, either by increasing sighs to improve regulation in case of a lack of sighing, or by decreasing sighs to restore regulation in case of excessive sighing. Finally, a research agenda on the psychology of sighs is presented.

Keywords: Sighsemotionsregulationflexibility

2. Sighing as a maladaptive behavior

Physiologically, complex breathing patterns serve to maintain blood gas levels consistent with metabolic need (Ben‐Tal & Tawhai, 2013). Breathing patterns resulting in deviations from normoxia and normocapnia, may cause respiratory symptoms. However, respiratory symptoms caused by dysfunctional breathing patterns can also occur in the presence of efficient gas exchange (Courtney and Cohen, 2006, Hornsveld et al., 1996, Hornsveld and Garssen, 1997, Vlemincx et al., 2012). While the term ‘dysfunctional breathing’ has been long used for a variety of maladaptive breathing patterns, recently, a classification system has been proposed to better understand and define dysfunctional breathing patterns (Boulding, Stacey, Niven, & Fowler, 2016). One type of dysfunctional breathing is periodic sighing (Boulding et al., 2016), also known as sigh syndrome, sighing dyspnea or sighing breathing (Aljadeff et al., 1993, Hurvitz and Weinberger, 2021, Sody et al., 2008, Wong et al., 2007, Wong et al., 2009), which consists of frequent sighing leading to hyperventilation-induced hypocapnia and associated respiratory symptoms.

Sighing more frequently than normal has been associated with various disease states. Sigh frequency in chronic low back pain patients is higher than in depressed and healthy controls, and correlates with pain ratings across periods of sitting, standing, reclining and walking (Keefe & Hill, 1985). In patients with traumatic brain injury, sighing is a frequent pain behavior, observed more during nociceptive exposure (compression of the nail bed), than during baseline, recovery and non-nociceptive exposure (non-invasive blood pressure measurements) (Nazari et al. 2018). In an ambulatory study in rheumatoid arthritis patients, sighing was associated with depression, yet not experienced pain (Robbins, Mehl, Holleran, & Kasle, 2011). Furthermore, while not a disease state, sighing is considered a symptom of motion sickness related to nausea (Leung & Hon, 2019).

In addition, sighing is associated with respiratory disease. Frequent sighing was present in a case of difficult-to-treat asthma (Prys-Picard, Kellett, & Niven, 2006). In this patient, sighs increased during exercise, and decreased after breathing retraining. In patients with respiratory disease, sighing co-occurred with emotional states (Stevenson & Ripley, 1952). In patients with so-called ‘hyperventilation syndrome’, sigh rate was higher during quiet sitting compared to healthy controls (Han et al., 1997), and while listening to soft music compared to healthy controls and asthmatics (Hormbrey, Jacobi, Patil, & Saunders, 1988).

Furthermore, the association between anxiety disorders and frequent sighing has been well established in laboratory studies; persons with panic disorder, post-traumatic stress disorder and chronic anxiety, sigh more frequently than (healthy) controls during quiet sitting and resting periods (Abelson et al., 2001, Abelson et al., 2008, Abelson et al., 2010, Blechert et al., 2007, Han et al., 1997, Schwartz et al., 1996, Tobin et al., 1983, Wilhelm et al., 2001a, Wilhelm et al., 2001b). Furthermore, the frequent sighing in panic disorder patients has been associated with chronic hypocapnia (Wilhelm et al., 2001a) and respiratory dysregulation indicated by high respiratory irregularity (Abelson et al., 2001, Martinez et al., 2001, Yeragani et al., 2002), suggesting that panic disorder patients sigh ‘excessively’ (i.e. sigh in excess of metabolic need). Importantly, however, it should be noted that these findings in anxiety disorders were observed in experimental laboratory studies, and have not been replicated in ambulatory studies. In ambulatory studies, there is no evidence that excessive sighing occurs in panic disorder (Pfaltz et al., 2009, Pfaltz et al., 2010). In addition, an ambulatory study did not find evidence for a relationship between sighing and dispositional negative emotionality (Danvers et al., 2021).

These findings could potentially, in part, be explained by the fact that ‘baselines’ or quiet sitting, resting laboratory conditions do not necessarily represent daily life (Wilhelm & Grossman, 2010). While research labs are commonly unfamiliar to participants (e.g. unfamiliar rooms, equipment, procedures, experimenters), daily life is the opposite. Previous studies have shown that panic disorder patients show increased neurobiological stress reactivity in response to contextual stressors, among which novelty (Abelson, Khan, Liberzon, & Young, 2007). Accordingly, quiet sitting and resting baseline measurements in the laboratory may constitute contextual stress or anxiety in persons with panic disorder. This reasoning would support a relationship between excessive sighing and state anxiety (which we will discuss in more detail below), rather than dispositional anxiety.

This rationale may help to understand why frequent sighing occurs in the disease states described above. We propose that the sigh is not only an important regulator of respiration (e.g. blood gases and lung compliance), but also an often overlooked contributor to the homeostatic regulation of psychological states, including stress, emotions (e.g. anxiety), and perceived symptoms and sensations (e.g. pain, dyspnea, nausea) (Vlemincx et al., 2010, Vlemincx et al., 2013). This would implicate that sighs occur frequently during these psychological states, and therefore, may become a byproduct of these psychological states associated with disease states. While sighs may be adaptive regulation mechanisms as long as their frequency matches metabolic demand, sighs may become maladaptive when occurring excessively. Excessive sighing may result in chronic hypocapnia (Wilhelm et al., 2001a), which may lead to widespread bodily symptoms (including autonomic, respiratory, cardiac, motor and emotional symptoms), overlapping with symptoms in a broad range of disease states, such as chronic pain, respiratory and cardiovascular disease, anxiety and neurological disorders. In turn, these bodily symptoms may require further regulation, and therefore further increase sighing, initiating a vicious cycle of emotions, symptoms and sighs. In other words, while sighs consistent with metabolic need may be adaptive to regulate psychological states, excessive sighs may exacerbate symptoms in various disease states. Below, we will detail the adaptive role of sighs.