Definition and Prevalence
Psychiatric symptoms such as low mood, emotional distress or non-specific psychological distress and psychiatric conditions, such as depressive mood disorders are more common in patients with life limiting illnesses than in the general population. [4,6,7] In Australia approximately 6.2 per cent of the general adult population is diagnosed and treated for depression.  Prevalence rates of depression for people with end stage cancer is estimated at 21 per cent,  in dementia at 15 per cent,  in heart failure at 20 per cent,  in end stage renal disease at 25 per cent,  and in end stage liver failure as high as 64 per cent.  Depression has been identified as a common symptom for those living in residential aged care facilities with prevalence rates as high as 44 per cent. [12,13] Depression has been identified as one of 11 common symptoms in a review of end-stage patient symptoms across five diseases.  The prevalence of depression in caregivers of patients is also higher than the general population, with estimates as high as 46 per cent.  Patients and their caregivers accessing palliative care services have been identified as having undiagnosed psychiatric symptoms and psychiatric conditions. [4,7,16]
In the palliative care setting the presence of emotional distress and non-specific psychological symptoms is common, understandable, and considered normative. [1,2] Screening and managing psychological distress is an integral part of the palliative care approach. Categorising different levels of emotional distress, anxiety and depression can be difficult and diagnosing psychiatric conditions, such as depressive mood disorder can be more difficult in advanced palliative disease because symptoms of other conditions, such as advancing or comorbid disease, may appear similar to symptoms of depression. Initial screening for psychiatric symptoms or conditions required a comprehensive clinical assessment that is based on the Diagnostic and Statistical Manual of Mental Health Disorders- Fifth edition (DSM- 5).  There is no one recommended screening or assessment tools for depression in palliative care.  A number of systematic reviews have examined the use of validated tools in various populations in the palliative care or end stage illness setting. [1,2,18-20] The Edmonton Symptom Assessment System, [1,18] the Beck Depression Inventory,  and the Hospital Anxiety and Depression Scale [2,19] are well known instruments and have been applied within the palliative care context. Care should be taken when using these tools to allow for confounding elements and limited information these tools may have. A recent systematic review examined the use of the Two-Question Screen for older adults and found this to be comparable with other tools, such as the Geriatric Depression Scale.  A number of tools have been examined for use in children including the Beck Depression Inventory, the Hospital Anxiety and Depression Scale and the Children’s Depression Inventory. 
The treatment approach used for a patient’s depression will be guided on the severity of symptoms and the estimated course of their illness. Many pharmacological interventions take some time to reach therapeutic effect and are therefore not appropriate in the last weeks of life.  Serotonin-norepinephrine reuptake inhibitors (SNRIs) can take between four to six weeks to reach optimal effect, while selective serotonin reuptake inhibitors (SSRIs) are slightly faster.  No one medication has been found to be more effective than another, although consideration should be given to side effect profiles of individual drugs. [5,22]
Similar to pharmacological approaches, non-pharmacological treatment approaches to depression take time to provide optimal therapy. Cognitive behavioural therapy (CBT), mindfulness interventions and acceptance and commitment therapy (ACT) are all recognised as potential therapeutic interventions in depression but take skilled practitioners, time to provide optimal therapy and are often best used in combination with pharmacotherapy when symptoms are severe. [1,23] Early referral to treatment services may be beneficial.
There is low quality evidence for non-pharmacological interventions in specifically treating depression in the palliative care context.  There may, however, be individual benefit to a patient depending on the severity of their situation and their particular clinical circumstances. A recent meta-analysis showed some benefit for CBT interventions for family and carers of patients with dementia and another demonstrated positive outcomes for ACT in a similar cohort.  Mindfulness interventions had limited evidence in caregivers but does show promise.  There does not appear to be any significant difference in outcomes if CBT interventions are delivered to family and carers as face to face or on-line interventions. 
Undiagnosed and untreated depression can have adverse effects on the quality of life for people accessing palliative care services and their families.  Depression will reduce a person’s quality of life as well potentially effecting their prognosis. The role of culture in the development of depression in a palliative care setting is not well understood. 
- Guidelines for identifying and managing depression are available. [1,27]
- While no screening tools for depression are recommended for use in a palliative care setting some tools that are validated in other populations may be useful, but consideration should be given to the complexity of the possible confounded items or limited information these tools may have. [1,20]
- Identifying depression may be more difficult in advanced palliative disease because symptoms of other conditions, such as advancing or co morbid disease, may appear similar to symptoms of depression. Conditions such as pain, or drug withdrawal, electrolyte imbalances and reactions to medication should be considered and treated if possible. 
- Treatment options for depression in patients with life limiting illnesses should be tailored to the symptom severity, patients’ clinical condition and prognosis.
- There is limited research to draw clear conclusions or consensus about the conceptualisation, assessment and management of depression in a palliative care setting. [3,8]
- Screening tools for depression and distress in the palliative population have been adapted from other groups and more research is need to validate them.
- The cultural influence on the expression of depression at the end of life is not clearly understood. 
- There is increasing evidence that reminiscence therapy may be effective at reducing depressive symptoms in people with dementia but more research is needed.