Table 2.

Definitions of mental pain underlying each measure of mental pain

	Definitions of mental pain
The Psychological Pain Assessment Scale Shneidman 1999	Definition given in the scale’s instructions: “Psychological pain is the same as somatic or physical pain, It is how you feel as a person; how you feel in your mind or heart. It refers to how much you hurt as a human being. It is mental suffering; inner torment. It is called psychache. Psychache refers to hurt or misery. It is the pain of shame, or guilt, or grief, or humiliation, or hopelessness, or loneliness, or sadness, or anguish. It is how you feel inside. It is an ache in the mind”. The author’s definition: ‘Psychological pain is the introspective experience of negative emotions such as anger, despair, fear, grief, shame, guilt, hopelessness, loneliness and loss—psychache’.
The Psychache Scale Holden 2001	Definition given in the scale’s instructions: “A hurting feeling inside, often described as pain you feel in your heart or mind. It indicates how much you hurt emotionally or mentally”. The authors had no specific definition and thus relied on Shneidman’s: 'Shneidman (1993) has asserted that the cause of suicide is psychache, that is, pain associated with psychache. This psychological pain is an aversive state that encompasses shame, guilt, humiliation, loneliness, fear, angst, dread, anguish, etc. When psychache surpasses an individual’s threshold for tolerance, it will cause suicidal behaviour’.
The Orbach and Mikulincer Mental Pain Scale Orbach and Mikulincer 2003	No definition given in the scale’s instructions. The author’s definition: 'Mental pain is defined as a wide range of subjective experiences characterised as an awareness of negative changes in the self and in its functions accompanied by negative feelings. Different factors reflect a distinct negative modification in self-image, self-definition, and self-functioning, tapping a different experiential aspect of these changes'.
The Tolerance of Mental Pain Scale Orbach 2004 (unpublished) Meerwijk 2019 (10-item version)	No definition given in the scale’s instructions. No specification of what is mental pain but a definition of the tolerance of mental pain. 'Tolerance for psychological pain refers to the ability to endure psychological pain'.
The Physical and Psychological Pain Scale Visual Analogue Scale Olié 2009	No definition given in the scale’s instructions: 'Instructions are purposely limited to simple sentences and no explicit definition is given'. The authors had no specific definition and thus relied on the definition of Shneidman: ‘Psychological pain or “psychache” is a central feature of mental disorders. It is defined as “the introspective experience of negative emotions such as dread, despair, fear, greed, shame, guilt, frustrated love, loneliness and loss”’ (Shneidman 1996).
The Mee-Bunney Psychological Assessment Pain Scale Mee and Bunney 2011	Definition given in the scale’s instructions: 'Intense psychological (mental pain) is a feeling which is experienced as unbearable torment. It can be experienced during a psychiatric disorder or a tragic loss such as the death of a child'. The authors' definition: 'In this study, intense “unbearable” psychological (mental) pain is defined as an emotionally based extremely aversive feeling which can be experienced as torment. It can be associated with a psychiatric disorder or with a severe emotional trauma such as the death of a child’.
The Three-dimensional Psychological Pain scale Li 2014	No definition given in the scale’s instruction. The authors had no specific definition and thus relied on the definition of Shneidman: 'Psychological pain, or psychache, has been defined as the “introspective experience of negative emotions such as dread, despair, fear, grief, shame, guilt, frustrated love, loneliness and loss” (Shneidman 1996), and is a common theme in suicide notes'.
The Mental Pain Questionnaire Fava 2016	Definition in the scale’s instruction: Mental or psychological pain is an experience that is part of life. It is different from physical pain. Definition of the authors: ‘Mental pain may be worse than most forms of physical pain, because it is not localised and often has no apparent reason. Grief provides an example of the sense of emptiness, loss of meaning and suffering that mental pain entails’.
The Unbearable Psychache Scale Pachkowski 2019	No definition given in the scale’s instructions. No specific definition of the authors, hence they relied on the definition of Shneidman: ‘First proposed by Shneidman, psychache refers to “the hurt, anguish, soreness, aching, psychological pain in the psyche, the mind”’ (Shneidman 1993).
The Psychic Pain Scale Lewis 2020	No definition given in the scale’s instructions. Definition of the authors: ‘Nearly all definitions of psychological pain focus on the central experience of overwhelming negative affect, and the devastating combination of experiencing this emotional state as both unbearable and impossible to resolve. Definitions of psychological pain in a general sense have typically included negative affect labels such as shame, sadness, and despair, and terms that allude to a sense of compromised mental integrity and psychological boundedness, such as disintegration, emotional flooding, and loss of control’.

We extracted the definition of mental pain proposed (1) in the instructions of each of the 10 scales if any and (2) provided in the paper cited in the left column.