Lovesickness refers to an informal affliction that describes negative feelings associated with rejection, unrequited love or the absence of a loved one. It can manifest as physical as well as mental symptoms. It is not to be confused with the condition of being lovestruck, which refers to the physical and mental symptoms associated with falling in love. The term lovesickness is rarely used in medical or psychological fields.

Many people believe lovesickness was created as an explanation for longings, but it can be associated with depression and various mental health problems.

Frank Tallis, a researcher in the topic of love and lovesickness, suggests in his 2005 article that lovesickness occurs when one is “truly, madly, deeply” in love and should be taken more seriously by medical professionals. Similarly, health experts agree that lovesickness has been known to kill and the diagnosis process should be taken more seriously. Symptoms of lovesickness are usually misdiagnosed for various other diseases or mental health issues such as OCD, this is because love sickness is less commonly recognized as a mental health issue in itself even though lovesickness is an extremely common, widespread disease.

Tallis includes a list of common symptoms of love sickness:

- Mania - an abnormally elevated mood or inflated self-esteem

- Depression

- Nausea

- Tearfulness

- Insomnia, which may lead to fatigue

- Lack of concentration

- Loss of appetite or overeating

- Hopelessness and/or helplessness

- Stress - high blood pressure, pain in chest and heart, acute insomnia; sometimes brought on by a "crush"

- Obsessive-Compulsive disorder - Preoccupation and hoarding valueless but superstitiously resonant items

- Psychologically created physical symptoms, such as upset stomach, change in appetite, insomnia, dizziness, and confusion

- Chronic neck pain, body tremors, intrusive thoughts, frequent flashbacks.

- Rapid mood swings

According to Tallis, many symptoms of being lovesick can be categorized under the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) and the ICD-10 (International Classification of Diseases). Obsessive-Compulsive disorder (OCD) is a symptom of lovesickness because it includes a preoccupation, this would include constantly checking one's cellphone, Facebook, the hoarding of valueless items, etc. A further study conducted by Italian Psychiatrist Donatella Marazitti found that when people fall in love their estimated serotonin levels drop to levels found in patients with OCD, this level is significantly lower than that of an average or healthy person.

Psychogenic pain, also called psychalgia, is physical pain that is caused, increased, or prolonged by mental, emotional, or behavioral factors.

Headache, back pain, or stomach pain are some of the most common types of psychogenic pain. It may occur, rarely, in persons with a mental disorder, but more commonly it accompanies or is induced by social rejection, broken heart, grief, lovesickness, or other such emotional events.

Sufferers are often stigmatized, because both medical professionals and the general public tend to think that pain from psychological source is not "real". However, specialists consider that it is no less actual or hurtful than pain from other sources.

The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, "or described in terms of such damage"" (emphasis added). In the note accompanying that definition, the following can be found about pain that happens for psychological reasons:

Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain.

Medicine refers also to psychogenic pain or psychalgia as a form of chronic pain under the name of "persistent somatoform pain disorder" or "functional pain syndrome". Causes may be linked to stress, unexpressed emotional conflicts, psychosocial problems, or various mental disorders. Some specialists believe that psychogenic chronic pain exists as a protective distraction to keep dangerous repressed emotions such as anger or rage unconscious.

It remains controversial, however, that chronic pain might arise purely from emotional causes. Treatment may include psychotherapy, antidepressants, analgesics, and other remedies that are used for chronic pain in general.