Inclusion Criteria:  Each patient must meet all of the following criteria to be enrolled in this trial:  Is between the ages of 4 - 18 years at the time of randomization. Meet diagnostic criteria for FASD or at risk of FASD according to the Australian Guide to the diagnosis of FASD. Is a patient of VicFAS or Developmental Paediatrics (Monash Health). Has a diagnosis of ADHD according to the DMS-IV criteria. Be on a stimulant medication for treatment of ADHD symptoms. Be on a stimulant medication as a primary treatment for ADHD. Be on a stable dose of stimulant medication for at last 1 month prior to the study. Provide a signed and dated informed consent form / and has a legally acceptable representative capable of understanding the informed consent document and providing consent on the participant's behalf. If seen by VicFAS/Developmental paediatrics between August 2019 - study commencement date), parent/guardian must have provided verbal or written consent to the VicFAS database PICF and selected 'yes' to the optional consent for contact for 'future research'.  Exclusion Criteria:  Exclusion criteria will include any of the following:  Inability to read or speak sufficient English for either child or parent/guardian to complete assessment tasks. Be on a medication for treatment of ADHD symptoms that is a medication other than stimulants as a primary treatment for ADHD. Allergy/sensitivity to Starcke 1500 (Maize Starch and Pregelatinised Maize Starch). Unable to swallow capsules. Intracranial symptoms or pathology such as epilepsy, hydrocephalus, diagnosed traumatic. brain injury or progressive intracranial tumours that may impact cognitive and behavioural function (children with asymptomatic or static lesions will be eligible). An abnormal ECG result at the time of screening deemed clinically significant by study physician. Presence of a significant comorbid psychiatric or psychological (excluding ADHD, oppositional defiant disorder, conduct disorder and pervasive development disorder/autism spectrum disorder) including depressive disorder, anxiety disorder, psychotic disorder, suicidality, Tic disorder, anorexia or bulimia nervosa Has a known hypersensitivity to starch or other compound relevant to placebo/capsules. Has had treatment with any other investigational drug within 4 weeks prior to randomisation. If the participant is known to be pregnant, they cannot take part in this research project. Parent/guardian not consenting to contact with paediatrician or school. Is deemed by their treating paediatrician to be medically unsafe for trial participation. Child's school unwilling to participate in outcome assessments.