LO5 study: The investigators are inviting a new group of youth (ages 7-16) who have been recently diagnosed with type 1 diabetes and their non-diabetic siblings. These youth will complete cognitive tests and a MRI scan of the brain. This scan uses strong magnets to obtain pictures and does not involve any radiation or injections. The investigators will recruit patients within three months of their diagnosis date. The study entails 1 study visit that lasts 3.5 hours. Evening and weekend times are available. The investigators plan to enroll 135 participants.

HY5 study: The investigators are inviting a cohort of youth and young adults (ages 9-21) with type 1 diabetes and their non-diabetic siblings for a follow-up to a study they have already completed. This group of people will complete several memory and thinking tests along with several MRI scans of their brain, just as they did at their previous visits. The investigators plan to enroll 150 participants.

LO5:

Inclusion Criteria for Participants with Type 1 Diabetes:

• Between the ages of 7 and 16
• Diagnosed with type 1 diabetes within 3 months

Inclusion Criteria for Participants without Type 1 Diabetes:

• Between the ages of 7 and 16

Exclusion Criteria for Participants with Type 1 Diabetes:

• Pregnant or lactating
• Chronic disease other than T1DM, well-controlled asthma, or Hashimoto's thyroiditis
• Other current serious medical illness
• Psychiatric illness
• Psychoactive drug dependence
• Neurological illness (except T1DM-related): stroke, seizure, major loss of consciousness, head injuries, encephalitis, or hydrocephalus, blindness, deafness
• Use of psychoactive medications or exposure to neuroleptics (except that exposures of less than 1 month, occurring more than 5 years ago, will be allowed)
• Use of dopamine depleting agents or stimulants such as Ritalin, Cylert, Adderall
• Pre-maturity at birth of more than 4 wks early with complications (e.g. on respirator at NICU)
• Inability to complete MRI scan (e.g. claustrophobia, metal implants)
• Full set (top and bottom) of orthodontic braces (Half set braces, fillings, and retainers are OK)

Exclusion Criteria for Participants without Type 1 Diabetes:

• Same as above (except cannot have type 1 diabetes)

HY5: Must have been a participant in our earlier study.

LO5: Youth with type 1 diabetes (T1DM) between the ages of 7-16 who have been diagnosed within the previous 3 months. Non-diabetic siblings of the participants with T1DM aged 7-16 years old.

HY5: Youth and young adults (ages 9-21) who have already completed an earlier study with the lab.