Dr Onyema trained in psychiatry in Ireland and obtained his membership with Royal College of Psychiatrist (UK). He also completed Masters in Medical Science degree with National University of Ireland Galway. He then relocated to New Zealand and Australia and became a Fellow of the Royal Australia New Zealand College of Psychiatrist.
Since moving to Australia, he has worked mainly on the Central Coast and North Sydney LHD. He has worked in broad range of areas in Mental Health. His particular clinical interest is working with adults presenting with psychiatric problems; Psychotic disorders, mood disorders, anxiety disorders, personality and adjustment disorders. Dr Onyema uses both pharmacological and psychological interventions when treating patients.