The Human body is made up of essential organs, which work together for adequate functioning and maintaining homeostasis. Among these organs, the brain is the most vital organ which controls every part of the body and fires responses against stimuli and perceives pain. Pain is an instinctive and a protective mechanism essential for survival. It is a complex human phenomenon that afflicts mankind. It is probably the most common symptom to seek medical consultation. According to the National Institute of health, the English word 'Pain' probably came from the old French word 'Peine' which means punishment. In prehistoric times, it was believed that pain is associated only to the tissue damage. To support this, the Medical dictionary defines pain as “a variably unpleasant sensation associated with acute or potential tissue damage”. Moreover, the International Association for the study of pain defines it as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” In addition to that, according to Davis (2013), pain is “a sensation in which an individual experiences discomfort, distress, or suffering due to irritation of sensory nerves.” Pain is considered a subjective feeling which differs from person to person. According to Rodriguez (2011), everyone has different pain perception, and the meaning of pain is also different from one person to another. This reflects the biological aspect of pain, but currently different theorists have made a great contribution on the pain perceptions that varies among people.

The experience and expression of pain is extremely influenced by biological and other factors as well. This includes personal factors, social factors, and psychological factors (Skevington 1995). Furthermore, Psychological factors such as emotional and situational factors that exist when we experience pain can extremely alter the strength of pain perception (McGrath, 1994). A client with an amputed toe, when knows about his sister's death, his pain intensifies. The triggering factor here is totally psychological. These all factors play a fundamental role in assessing and managing pain in successful ways.

This study comprises of complex literature analyses, which aimed to explore a variety of different factors related to pain, including models, theories, and its relevance to the practice of Nursing. Thorough understanding of pain perception is required to enable Nursing and other healthcare professionals to adequately identify and act promptly to provide holistic and quality-centric care.

This article encircles a literature review about the management and classification of various factors that are involved in influencing the patient's pain perception. This 'view' is gathered from a deep reflection on the available literature from various online databases, such as PUBMED, CINAHL, MEDLINE, and Google Scholar, and other relevant research articles published until 2019.

Firstly, it is believed that sociocultural factor controls one's pain perception. To support this, Skevington (1995) proposed a model of psychosocial factors that are associated with different pain perceptions. This model consists of four different levels. The first level shows the relation between behavior and society. In this level, social schema, personal motivation, social and personal emotions, individual representations, etc., are included. Moreover, researches provide evidence that different social and cultural factors greatly influence pain thresholds and pain tolerance levels. In the Hispanic culture, stoicism is highly prized (Hadjistavropoulos & Kenneth, 2008). Whereas, in other cultures, describing the pain in an extended way is preferred (Peacock & Patel, 2008). On the other hand, most people don't like to seek medical attention until the symptoms appear. However, opposite to popular belief, people do not always seek help for their health when they are “sickest,” but are more likely when the symptoms interfere with their lives (Hadjistavropoulos & Kenneth, 2008).

Researches have also emphasized upon some psychological traits such as catastrophizing which mean perceiving pain as threatening. Sullivan and colleagues theoretically examined the concept of catastrophizing and suggested that social factors were concerned in the development and later maintenance of catastrophizing (Quartana, Campbell, & Edwards, 2009). The second level of this model is interpersonal behaviors, which include selfefficacy; it is defined as the person's belief about his potentials. Jensen, Turner, Romano, and Karoly (1991) reported a strong relationship of self-efficacy with coping in one of his studies done on 114 chronically ill patients. Enhancing perceptions of self-efficacy in them has yielded significant and clinically meaningful results (Jensen et al., 1991). The third level is associated with the group. This level caters different groups of people which can influence perceptions of pain. For instance, boys are considered strong. If in a peer group, a boy is feeling pain so all of his peers would stigmatize that boy to be weak. This is how groups impact one's pain perception and expression. It is also said that white people are more pain sensitive and willing to report pain than typical Asian, Hispanic, and black individuals, respectively (Wandner, Scipio, Hirsh, Torres, Robinson, 2012). The last level represents health culture, quality of life, economic beliefs about health, etc. Hence, this model greatly influences an individual's pain perceptions and expressions.

Secondly, gender also plays a vital role in pain perception. Researches reveal that perception and expression of pain are gendered specific. Besides, pain perception and response are divided into two categories; Stoic and Emotive (Racine et al., 2012). Stoic people are those who are less expressive and can tolerate pain to a great extent while Emotive people are those who like to ventilate their feelings of pain and want people around them for support. In the Pakistani context, males are considered stoic and females are considered as emotive. It is believed that men are strong so they won't cry, but females are sensitive and emotional so they can express their pain easily. It has also been observed in the clinical setting that female has more frequent pain complaints than males and they require interventions to manage their pain. Researchers have also found that estrogen can act as a natural painkiller. Therefore, gender-specific pain assessment should be part of the plan of care (Bartley & Fillingim, 2013).

Thirdly, religion also influences pain perception. In Pakistani societies, it has been observed that Quranic verses are used to treat minor pains like headaches, backaches, etc. (Unruh, 2007). This is a common practice followed by almost all Islamic societies. According to them, it relieves their pain and stress. In Pakistani societies, it is also observed that faith healers are considered religious doctors who can benefit people relieving their pain. Moreover, spirituality and religious beliefs sometimes also develop a stigma among patient as they think that the illness is due to any kind of evil spirit or black magic. Such thinking of a patient could be very harmful and may lead to maladaptive coping strategies because it lowers a person's self-esteem and destroys the self-concept. A healthcare provider needs to discover such beliefs of patients and families and help them understand that this is due to altered physiological conditions and not a punishment of one's sins.

Additionally, culture also is an important aspect of perceiving pain as in Muslim culture, Shias show a greater tolerance level in the days of Muharram.

Moreover, a Cambodian patient might believe that without an injection, treatment is not enough whereas a Filipino or East Indian patient might reject pain medications altogether out of fear of harmful effects. Coping also varies culturally and this may be as significant as differences in perceptions of pain (Callister, 2003).

Besides that, analyses of age-related expectation of pain indicate that pain sensitivity diminishes with advanced age. Once an individual surpasses the age of 60, the incidence of pain is more than the double. With that, pain frequency increases with each decade (Miaskowski, 2000).

Lastly, Researchers have identified that genetics is also considered one of the aspects of pain perception. An alternative of the CACNG2 gene is considered as a risk factor for chronic pain after breast surgery. This gene is believed to control the excitability of neurons (Nissenbaum et al., 2010). Moreover, it has also been identified that alterations in the neural activity due to pain in the early development of a child may produce long term effects on future response and perception of pain (Walker et al., 2009).

History reveals that the two giants of ancient Greece, Aristotle and Plato were the first to consider pain not to be a sensory experience, but an emotional one. Aristotle described the pain as an evil spirit that enters the body through an injury. Long after Descartes, the pain was described as a mind-body split. Then later, the emphasis was on the bio psychosocial model, which highlights pain in a diversified manner. The model itself affirms that it has three dimensions; biological, psychological, and social. The same point of view was also given by Hadjistavropoulos and Craig (2004) who compared to either of the traditional biomedical and psychodynamic element. The bio psychosocial approach posits a much broader, multidimensional, and complex perspective on pain. Whereas, the biomedical model only focuses on biological processes. According to that model, Pain is the symptom of underlying tissue damage and psychological factors play a minimal role in pain perception (Keefe, Abernethy, & Campbell, 2005). According to Keefe et al. (2005), “Dissatisfaction with the traditional biomedical model of pain has led to developments of new pain theories”.

Recently researches have verified that pain is mainly a psychological phenomenon and psychological factors exert a great influence on the perception of pain. In addition, one of theories that define psychological aspects of the pain is the Gate Control Theory. According to this theory, the human spinal cord has several gates that provide a way for incoming impulses. The spinal gates receive impulses and then decide whether to open the gate or remain close. In a condition when it is open, it results in pain perception. Also, opening and closing of gates depend upon individuals' coping, his emotions and his attention towards the source of pain (Katz & Rosenbloom, 2015). Additionally, the Fear-Avoidance model explains the patient's transition from acute pain condition to a chronic state of depression, disability, and inactivity. This model claims that fear of pain is more disabling than the pain itself. It alters the patient's cognitive function, intensifies painrelated sensation, and disengages them from physical activity. This ultimately makes the patient prone to delayed recovery (Linton & Shaw, 2011). Similarly, Bustan et al. (2018) emphasized that people with good coping mechanism may suffer less despite enhanced pain than the ones who fear pain even with low pain. Furthermore, Personality disorders and traits which embroils deviation in affectivity, impulse control, cognition, and interpersonal functioning are responsible for deprived health, premature mortality, and poor outcomes in health.

Behaviorists also played a key role in perceiving pain. According to Belfer (2013), personality, sleep pattern, and mood can greatly influence pain sensitivity and behavior. Specifically, catastrophizing as one of the personality traits can amplify the intensity of pain in both clinical and experimental setting. With that, pain sensitivity increases 2 to 3 fold at the time of depression or anxiety. Moreover, altered sleep may enhance pain perception and mediate the effects of pain catastrophizing on clinical pain.

Pain is considered to be the 5^th vital sign of a person so it is the responsibility of a healthcare professional to help the individual in reducing distress. This can be done by teaching relaxation exercises, providing full information about the illness, performing mind diversional therapies, teaching adaptive coping strategies like CBT along with Acceptance and Commitment Therapy (ACT) as one of the newest iterations and providing mindfulness treatments. Incriminating the discussed intervention can aid in correcting the patient's thoughts and perceptions and building confidence in patients with a decrease in the feeling of hopelessness and helplessness. With that, rodent models can be inculcated while providing care to the patient. According to the models, physical therapy and socially enriched atmosphere can contribute greatly in overcoming fear, reducing pain behavior and normalizing brain function (Bushnell et al., 2015). During exercise, endogenous analgesia is activated due to a release of beta-endorphin from hypothalamus and pituitary, that in turn facilitates analgesic effects by activating μ-opioid receptors (Belfer, 2013). Above all, psychological self-efficacy model should be taken into account to treat the patient's pain. As per the model, patient's preferences, decision making, coping difficulties to deal with pains flareup should be taken into consideration to manage pain effectively (Linton & Shaw, 2011). Correspondingly, awareness and vigilance to a clinical characteristic of personality disorders in general healthcare should be given attention to providing optimal support to patients.

In conclusion, pain is the most distressing, unpleasant, sensory, and emotional experience, which greatly influences a person's life. Its perception and expression vary from one person to another. Moreover, researchers have identified that psychological factors play a fundamental role in assessing and managing pain. Some of the aspects of perceiving pains are gender, religion, social, cultural, and genetics. Furthermore, nursing practice has great importance to inpatient care. A nurse should approach the patient holistically and should understand the psychological factors and interventions to deal with an individual's pain perception.