However, these changes will likely only develop after chronic PPD associated with severe mental illness, as opposed to less severe forms of the disorder as seen in those with anxiety and affective disorders. PPD is also linked with significant reductions in insular cortex volume, although this may be caused by the secondary hyponatraemia. It has been suggested that these deficits lead to moderate to severe cognitive impairments, especially affecting working memory, verbal memory, executive function, attention and motor speed.Other areas with volume reductions (both white and grey matter) include:
Right posterior lobe
Right inferior temporal gyrus
Parahippocampal gyrus
Both left and right superior temporal gyri
Right cuneus
Left medial frontal gyryus and inferior frontal gyrus
Right lingual gyrus

Diagnosis
As a diagnosis of exclusion, a diagnosis of primary polydipsia may be the result of elimination of the possibility of diseases causing similar signs and symptoms, such as diabetes insipidus. Diagnosis may be complicated by the fact that chronic and extreme compulsive drinking may impair the response of the kidneys to vasopressin, thus reducing the kidneys ability to concentrate the urine. This means that psychogenic polydipsia may lead to test results (e.g. in a water restriction test) consistent with diabetes insipidus or SIADH, leading to misdiagnosis.Dry mouth is often a side effect of medications used in the treatment of some mental disorders, rather than being caused by the underlying condition. Such medications include antipsychotics, antidepressants, anticonvulsants, alpha agonists and anticholinergics. It should also be ensured that the thirst isnt caused by diuretic use (particularly thiazide diuretics), MDMA use, excessive solute intake or chronic alcoholism.
Stiff-person syndrome (SPS), also known as stiff-man syndrome (SMS), is a rare neurologic disorder of unclear cause characterized by progressive rigidity and stiffness. The stiffness primarily affects the truncal muscles and is superimposed by spasms, resulting in postural deformities. Chronic pain, impaired mobility, and lumbar hyperlordosis are common symptoms. SPS occurs in about one in a million people and is most commonly found in middle-aged people. A small minority of patients have the paraneoplastic variety of the condition. Variants of the condition, such as stiff-limb syndrome which primarily affects a specific limb, are often seen. SPS was first described in 1956. Diagnostic criteria were proposed in the 1960s and refined two decades later. In the 1990s and 2000s the roles of antibodies in the condition became more clear. SPS patients generally have GAD antibodies, which seldom occur in the general population. In addition to blood tests for GAD, electromyography tests can help confirm the conditions presence. Benzodiazepine-class drugs are the most common treatment; they are used for symptom relief from stiffness. Other common treatments include baclofen, intravenous immunoglobin and rituximab. There is a limited but encouraging therapeutic experience of hematopoietic stem cell transplantation for SPS. Signs and symptoms
Patients with stiff-person syndrome (SPS) experience progressive stiffness in their truncal muscles (torso muscles), which become rigid and stiff because the lumbar and abdominal muscles engage in constant contractions. Initially, stiffness occurs in the thoracolumbar paraspinal and
abdominal muscles. It later affects the proximal leg and abdominal wall muscles.