Sadness is an emotional pain associated with, or characterized by, feelings of disadvantage, loss, despair, grief, helplessness, disappointment and sorrow. An individual experiencing sadness may become quiet or lethargic, and withdraw themselves from others. An example of severe sadness is depression, a mood which can be brought on by major depressive disorder or persistent depressive disorder. Crying can be an indication of sadness.Sadness is one of the six basic emotions described by Paul Ekman, along with happiness, anger, surprise, fear, and disgust. : 271–4

Childhood
Sadness is a common experience in childhood. Sometimes, sadness can lead to depression. Some families may have a (conscious or unconscious) rule that sadness is "not allowed", but Robin Skynner has suggested that this may cause problems, arguing that with sadness "screened off", people can become shallow and manic. : 33, 36  Pediatrician T. Berry Brazelton suggests that acknowledging sadness can make it easier for families to address more serious emotional problems. : 46, 48 Sadness is part of the normal process of the child separating from an early symbiosis with the mother and becoming more independent. Every time a child separates a little more, he or she will have to cope with a small loss. If the mother cannot allow the minor distress involved, the child may never learn how to deal with sadness by themselves.
All individuals tested with classical early-onset, SLC6A3-related DTDS display raised homovanillic acid (HVA) levels with normal 5-hydroxyindoleacetic acid (5-HIAA, a serotonin metabolite) levels. DTDS patients demonstrate a HVA:5-HIAA ratio of 5.0-13.0, above the normal range of 1.0-4.0. In addition, the patients have normal pterin profiles.Mutant constructs of human dopamine transporter can be used for in vitro functional analysis of any particular mutants dopamine uptake and cocaine-analogue binding. Treatment
A multidisciplinary approach to long-term management of this progressive disorder is optimal. Treatment can be split into three categories: treatment of DTDS manifestations, prevention of secondary complications, and monitoring of overall disease progression. Manifestations
Treatment to control the chorea and dyskinesia in the early stages of DTDS is done with tetrabenazine and benzodiazepines. The dystonia is more difficult to control and the first-line agents include pramipexole and ropinirole; adjuncts include trihexyphenidyl, baclofen, gabapentin, and clonidine for severe dystonia, and chloral hydrate and benzodiazepines for exacerbations of dystonia or status dystonicus. Prevention of secondary complications
Regular physiotherapy is recommended to reduce the risk of contractures, shortening and hardening of the muscles. Feeding may become difficult and alternative feeding strategies including nasogastric tubes or percutaneous endoscopic gastrostomies may become necessary due to progressive bulbar dysfunction. The influenza vaccine is used in combination with prophylactic antibiotics to prevent chest infections. Monitoring
Patients are evaluated every six to 12 months for early evidence of hip dislocation and spinal deformities. Risk of pulmonary aspiration is evaluated with regular swallowing assessments. Nutritional assessments are performed regularly to ensure adequate caloric intake.